A chip-level underfill adhesive suitable for large-size chip packaging and a preparation method thereof

Abstract

The application discloses a chip-level underfill adhesive suitable for large-size chip packaging and a preparation method thereof, and the chip-level underfill adhesive comprises the following components in parts by weight: 5-10 parts of self-synthesized multifunctional epoxy resin, 40-50 parts of epoxy resin, 3-6 parts of coupling agent, 2-4 parts of black paste, 50-70 parts of filler and 20-30 parts of curing agent. The chip-level underfill adhesive has excellent flow performance, can meet the operation requirement of large-size chip packaging, has excellent toughness and high-temperature modulus, effectively guarantees the reliability of the chip-level underfill adhesive under the cold and hot cycle impact condition, has low CTE, avoids problems such as filling cracking caused by too large difference in thermal expansion coefficients of different materials, and has high thrust strength to the silicon wafer under the condition of 260 DEG C after the product and the silicon wafer are cured and bonded and are placed in an Uhast environmental chamber for 96 hours, thereby effectively solving the problem that the traditional chip-level underfill adhesive is delaminated from the substrate under the high-temperature and high-humidity environment.

Description

Technical Field

[0001] This invention belongs to the field of adhesives, specifically relating to a chip-level underfill adhesive suitable for large-size chip packaging and its preparation method. Background Technology

[0002] Flip-chip packaging is one of the main chip packaging technologies currently available. The chip faces down and interconnects with the substrate, with the chip electrodes and substrate wiring layers securely soldered together using solder joints. Flip-chip technology features high packaging density, short interconnect distances, and excellent electrical performance and reliability. Chip-level underfill, an essential material in flip-chip packaging, fills the gap between the chip and substrate connected by solder balls through capillary action, firmly integrating the chip, solder bumps, and substrate into a unified whole. It seals and protects the solder joints, reducing stress caused by the mismatch in thermal expansion coefficients between the chip and substrate. Chip-level underfill plays a crucial role in improving the reliability of IC packaging.

[0003] Large-size chip packaging places more stringent demands on the functionality of chip-level underfill adhesives. The market for chip-level underfill adhesives used in large-size chip packaging is largely monopolized by foreign companies, making the domestic development of such adhesives extremely urgent. Firstly, the stress caused by the mismatch in thermal expansion coefficients between large-size chips and the substrate is far greater than that of small- and medium-sized chips. Therefore, chip-level underfill adhesives used in large-size chip packaging must have low CTE (Coefficient of Thermal Expansion). Secondly, large-size chip packaging requires a larger filling area, demanding that the applicable chip-level underfill adhesive possess excellent flowability and filling performance. Most importantly, large-size chip packaging places stricter and more demanding reliability requirements on chip-level underfill adhesives, requiring the applicable products to have excellent toughness and modulus, high adhesion strength to the silicon wafer, and better resistance to damp heat. However, simultaneously meeting all these functional requirements presents a significant challenge. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a method for preparing a chip-level underfill adhesive with excellent reliability suitable for large-size chip packaging. The resulting product simultaneously possesses excellent flow properties, low CTE, outstanding toughness, and excellent high-temperature modulus. After curing and bonding the product to a silicon wafer, it still exhibits high thrust strength to the silicon wafer even at 260°C after being placed in a Uhast environmental chamber for 96 hours. The product of this invention can fully meet the workability and reliability requirements of large-size chip packaging.

[0005] The specific technical solution is as follows:

[0006] One objective of this invention is to provide a reliable chip-level underfill adhesive suitable for large-size chip packaging and its preparation method, characterized in that it comprises the following components in parts by weight:

[0007] 5-10 parts of self-synthesized multifunctional epoxy resin, 40-50 parts of epoxy resin, 3-6 parts of coupling agent, 2-4 parts of black paste, 50-70 parts of filler, and 20-30 parts of curing agent.

[0008] The self-synthesized multifunctional epoxy resin is prepared from the following compounds:

[0009] (1) Bisphenolic compounds with aromatic aldehydes are prepared from the following raw materials: 8-10 parts of 4,4′-oxydiphenol, 650-750 parts of trifluoroacetic acid, 35-40 parts of hexamethylenetetramine, and 1000-1200 parts of hydrochloric acid.

[0010] (2) Vanillin-based imine compounds are prepared from the following raw materials: 22-25 parts of diaminomethylcyclohexane, 7-8 parts of vanillin, and 20-25 parts of ethanol.

[0011] (3) Bisphenolic compounds with aromatic imines are prepared from the following raw materials: 25-30 parts of vanillin-based imine compounds prepared above, 10-12 parts of bisphenolic compounds with aromatic aldehydes prepared above, and 35-55 parts of ethanol.

[0012] (4) The self-synthesized multifunctional epoxy resin is prepared from the following raw materials: 30-40 parts of the bisphenol compound with aromatic imine prepared above, 5-10 parts of benzyltriethylammonium chloride, 180-220 parts of epichlorohydrin, and 25-30 parts of sodium hydroxide solution.

[0013] Furthermore, the self-synthesized multifunctional epoxy resin is prepared by a four-step method. The first step is to react 4,4′-oxodiphenol with hexamethylenetetramine via a Duff reaction, thereby formylating 4,4′-oxodiphenol with hexamethylenetetramine to obtain a bisphenol compound containing aromatic aldehydes. The second step is to react diaminomethylcyclohexane with vanillin via an aldehyde-amine condensation reaction to obtain a vanillin-based imine compound. The third step is to react the bisphenol compound containing aromatic aldehydes with the vanillin-based imine compound via an aldehyde-amine condensation reaction to obtain a bisphenol compound with aromatic imines. The fourth step is to react the bisphenol compound with aromatic imines with epichlorohydrin via an epoxidation reaction to obtain a multifunctional epoxy resin.

[0014] The beneficial effects of the above-mentioned further solutions are as follows: The prepared multifunctional epoxy resin has four epoxy groups that can participate in curing and crosslinking. Under the action of the curing agent, it can form a three-dimensional network structure with the main epoxy resin, increasing the crosslinking density of the system and improving the modulus and impact resistance of the chip-level underfill adhesive. At the same time, the highly crosslinked polymer network can prevent the penetration of water molecules, has a low moisture absorption rate, and ensures the reliability of large-size chip packaging under high temperature and high humidity environments. The benzene ring structure and alicyclic structure of the self-synthesized multifunctional epoxy resin endow the material with outstanding high-temperature modulus and excellent thermal stability, enabling the chip-level underfill adhesive of the present invention to still have excellent bonding strength with the silicon wafer under high temperature conditions. The self-synthesized multifunctional epoxy resin has a polyether bond skeleton structure, which plays a positive role in improving the flexibility of the material after curing. With both excellent toughness and modulus, it effectively ensures the reliability of the chip-level underfill adhesive under thermal cycling shock conditions. The chip-level underfill adhesive of the present invention can fully meet the relevant reliability testing requirements of large-size chip packaging. The self-synthesized multifunctional epoxy resin contains multiple aromatic imines, which significantly reduces the exothermic capacity and total exothermic rate of the chip-level underfill adhesive during the curing process. This avoids problems such as separation and cracking between the product and the substrate and solder balls due to volume shrinkage and high heat release during curing. The self-synthesized multifunctional epoxy resin has multiple methylene structures, which have a positive effect on water resistance and thermal stability.

[0015] The structural formula of the self-synthesized multifunctional epoxy resin is as follows:

[0016]

[0017] The synthesis route of the self-synthesized multifunctional epoxy resin is as follows:

[0018]

[0019] Furthermore, the epoxy resin is one or a mixture of two or more of the following: aminophenol type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and naphthalene type epoxy resin. Preferably, the aminophenol type epoxy resin is JER630 from Mitsubishi Chemical Corporation, Japan; the bisphenol A type epoxy resin is preferably 850CRP from DIC Corporation, Japan; the bisphenol F type epoxy resin is preferably YDF8170 from Nippon Steel & Sumitomo Metal Chemicals Co., Ltd.; and the naphthalene type epoxy resin is preferably HP 4032D from DIC Corporation, Japan.

[0020] The beneficial effect of adopting the above-mentioned further solution is that by selecting different types of epoxy resins, the Tg point, bonding strength, tensile strength and modulus of the chip-level underfill adhesive can reach a balance point, resulting in excellent comprehensive performance.

[0021] Furthermore, the coupling agent is a silane coupling agent, specifically one or a mixture of two or more of 3-(2,3-epoxypropoxy)propylmethyldiethoxysilane, aminopropyltriethoxysilane, and phenylaminopropyltrimethoxysilane.

[0022] The beneficial effects of adopting the above-mentioned further solutions are: silane coupling agents help improve the wetting performance of chip-level underfill adhesive on the substrate and improve flowability; improve the compatibility between resin and filler; improve the wettability of chip-level underfill adhesive on the substrate and enhance bonding strength.

[0023] Furthermore, the black paste is a premix of carbon black and epoxy resin, specifically a premix of MA100 from Mitsubishi Corporation of Japan and 840 from DIC Corporation of Japan, with a ratio of MA100 to 840 of 2:8.

[0024] Furthermore, the curing agent is a liquid aromatic amine curing agent. The preferred liquid aromatic amine curing agent is diethyltoluene diamine, and more preferably, ETHACURE 100 from Albemarle Co., Ltd., Japan.

[0025] The beneficial effects of adopting the above-mentioned further solutions are: ensuring that the chip-level underfill adhesive has excellent flow properties, meeting the requirements of chip-level underfill adhesive for large-size chip packaging; and meeting the requirements of curing temperature and curing speed required for large-size chip packaging processes.

[0026] Further, the filler is spherical silica, preferably a composition of spherical silica with different particle sizes. Spherical silica A is preferably spherical silica with an average particle size of 1.5 μm after surface treatment with 3-glycidoxypropyltrimethoxysilane, more preferably SE5050-SEJ manufactured by ADMATECHS Co., Ltd. of Japan. Spherical silica B is preferably spherical silica with an average particle size of 0.5 μm after surface treatment with 3-glycidoxypropyltrimethoxysilane, more preferably SE2200-SEE manufactured by ADMATECHS Co., Ltd. of Japan. Spherical silica C is preferably spherical silica with an average particle size of 50 nm after surface treatment with 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, more preferably YA050A-JGP manufactured by ADMATECHS Co., Ltd. of Japan. The ratio of A:B:C in spherical silica is 15-25:2.7-5.2:0.5-1.5.

[0027] The beneficial effects of adopting the above-mentioned further solutions are: compared with non-spherical silica, spherical silica can make the chip-level underfill adhesive have better flowability when the filler content is the same; the combination of spherical silica micro powders with different particle sizes can maximize the amount of filler added when the viscosity is the same, so that the chip-level underfill adhesive has a lower CTE and ensures the reliability of large-size chip packaging.

[0028] The beneficial effects of this invention are as follows: The chip-level underfill adhesive of this invention has excellent flow properties, which can fully and quickly meet the operational requirements of large-size chip packaging and avoid defects formed during the flow curing process; it has low CTE, which reduces the stress generated at the solder joint due to the mismatch of the thermal expansion coefficients between the chip and the substrate, effectively ensuring the reliability of large-size chip packaging; more importantly, this product has both excellent modulus and toughness, ensuring excellent reliability of large-size chip packaging under thermal shock conditions; after curing and bonding with silicon wafers, the product of this invention still has high thrust strength to silicon wafers at 260°C after being placed in a Uhast environmental chamber for 96 hours, enabling large-size chip packaging to have excellent reliability in high temperature and high humidity environments. Detailed Implementation

[0029] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0030] The self-synthesized multifunctional epoxy resin is prepared as follows;

[0031] 8.9 parts of 4,4′-oxadiol and 700 parts of trifluoroacetic acid were added to a round-bottom flask and stirred. Then, 37 parts of hexamethylenetetramine were slowly added to the mixture, and the reaction was carried out at 90°C for 24 hours under an argon atmosphere. The resulting mixture was then slowly cooled to room temperature, and 1100 parts of hydrochloric acid were added and stirred for another 24 hours. The mixture was then extracted with dichloromethane, and the dichloromethane was washed three times with deionized water and once with brine to remove water-soluble impurities. The organic phase was then dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation. Finally, the solvent was completely removed in a vacuum oven at 120°C to obtain purified bisphenol compounds containing aromatic aldehydes.

[0032] 22 parts of diaminomethylcyclohexane were added to a round-bottom flask; subsequently, 7.6 parts of vanillin were dissolved in 20 parts of ethanol and added to the diaminomethylcyclohexane under nitrogen purging, and the mixture was stirred. The resulting mixture was then refluxed at 50°C for 3 hours, cooled to room temperature, and the solvent and unreacted diaminomethylcyclohexane were removed by vacuum drying. The remaining product was purified by single-solvent recrystallization from ethyl acetate to obtain vanillin-based imine compounds.

[0033] 27.6 parts of the vanillin-based imine compound prepared above were added to a round-bottom flask; subsequently, 10.3 parts of the aromatic aldehyde bisphenol compound prepared above were dissolved in 40 parts of ethanol, added to the round-bottom flask under nitrogen purging, and stirred. The resulting mixture was then refluxed at 60°C for 3 hours, cooled to room temperature, and the solvent in the reactants was removed by vacuum drying. The remaining product was then purified by single-solvent recrystallization from ethyl acetate to obtain the aromatic imine bisphenol compound.

[0034] To a three-necked flask, add 34 parts of the bisphenol compound containing aromatic imines prepared above, 4 parts of benzyltriethylammonium chloride, and 200 parts of epichlorohydrin, and stir at 80°C for 5 hours. After cooling to room temperature, add 4 parts of benzyltriethylammonium chloride and 27 parts of sodium hydroxide solution to the mixture, and continue stirring at room temperature for 8 hours. The product is then extracted three times with ethyl acetate, and the resulting ethyl acetate phase is washed three times with deionized water and brine, and then dried with anhydrous magnesium sulfate. The product is concentrated by filtration and evaporation; the concentrated product is then separated and purified by silica gel column chromatography to prepare a self-synthesized multifunctional epoxy resin.

[0035] Example 1

[0036] At room temperature, by weight, 10 parts of self-synthesized multifunctional epoxy resin, 20 parts of aminophenol type epoxy resin JER630, 10 parts of naphthalene type epoxy resin HP4032D, 20 parts of bisphenol A type epoxy resin 850CRP, 3 parts of aminopropyltriethoxysilane, 2 parts of black paste, 40 parts of spherical silica SE5050-SEJ with an average particle size of 1.5μm, 7.8 parts of spherical silica SE2200-SEE with an average particle size of 0.5μm, and 2.2 parts of spherical silica YA050A-JGP with an average particle size of 50nm were added to a mixing tank, stirred evenly, and degassed under vacuum. The premixed material was then subjected to a three-roll milling and curing process to ensure full impregnation of the filler. The premixed material was then mixed with 20 parts of liquid aromatic amine curing agent ETHACURE. 100 are sequentially added to a mixing vessel, stirred evenly, and then vacuumed to remove bubbles, thus obtaining the chip-level underfill adhesive suitable for large-size chip packaging of the present invention.

[0037] Example 2

[0038] At room temperature, by weight, 5 parts of self-synthesized multifunctional epoxy resin, 20 parts of aminophenol type epoxy resin JER630, 10 parts of naphthalene type epoxy resin HP4032D, 20 parts of bisphenol A type epoxy resin 850CRP, 3 parts of aminopropyltriethoxysilane, 2 parts of black paste, 40 parts of spherical silica SE5050-SEJ with an average particle size of 1.5μm, 7.8 parts of spherical silica SE2200-SEE with an average particle size of 0.5μm, and 2.2 parts of spherical silica YA050A-JGP with an average particle size of 50nm were added to a mixing tank, stirred evenly, and degassed under vacuum. The premixed material was then subjected to a three-roll milling and curing process to ensure full impregnation of the filler. The premixed material was then mixed with 20 parts of liquid aromatic amine curing agent ETHACURE. 100 are sequentially added to a mixing vessel, stirred evenly, and then vacuumed to remove bubbles, thus obtaining the chip-level underfill adhesive suitable for large-size chip packaging of the present invention.

[0039] Example 3

[0040] At room temperature, by weight, 10 parts of self-synthesized multifunctional epoxy resin, 20 parts of aminophenol type epoxy resin JER630, 10 parts of naphthalene type epoxy resin HP 4032D, 20 parts of bisphenol F type epoxy resin YDF8170, 3 parts of aminopropyltriethoxysilane, 2 parts of black paste, 40 parts of spherical silica SE5050-SEJ with an average particle size of 1.5 μm, 7.8 parts of spherical silica SE2200-SEE with an average particle size of 0.5 μm, and 2.2 parts of spherical silica YA050A-JGP with an average particle size of 50 nm are added to a mixing tank, stirred evenly, and degassed under vacuum. The premixed material is then subjected to a three-roll milling and curing process to ensure full impregnation of the filler. The premixed material is then mixed with 20 parts of liquid aromatic amine curing agent ETHACURE. 100 are sequentially added to a mixing vessel, stirred evenly, and then vacuumed to remove bubbles, thus obtaining the chip-level underfill adhesive suitable for large-size chip packaging of the present invention.

[0041] Example 4

[0042] At room temperature, by weight, 10 parts of self-synthesized multifunctional epoxy resin, 20 parts of bisphenol F type epoxy resin YDF8170, 10 parts of naphthalene type epoxy resin HP 4032D, 20 parts of bisphenol A type epoxy resin 850CRP, 3 parts of aminopropyltriethoxysilane, 2 parts of black paste, 40 parts of spherical silica SE5050-SEJ with an average particle size of 1.5μm, 7.8 parts of spherical silica SE2200-SEE with an average particle size of 0.5μm, and 2.2 parts of spherical silica YA050A-JGP with an average particle size of 50nm were added to a mixing tank, stirred evenly, and degassed under vacuum. The premixed material was then subjected to a three-roll milling and curing process to ensure full impregnation of the filler. The premixed material was then mixed with 20 parts of liquid aromatic amine curing agent ETHACURE. 100 are sequentially added to a mixing vessel, stirred evenly, and then vacuumed to remove bubbles, thus obtaining the chip-level underfill adhesive suitable for large-size chip packaging of the present invention.

[0043] Example 5

[0044] At room temperature, by weight, 10 parts of self-synthesized multifunctional epoxy resin, 10 parts of bisphenol F type epoxy resin YDF8170, 20 parts of aminophenol type epoxy resin JER630, 20 parts of bisphenol A type epoxy resin 850CRP, 3 parts of aminopropyltriethoxysilane, 2 parts of black paste, 40 parts of spherical silica SE5050-SEJ with an average particle size of 1.5μm, 7.8 parts of spherical silica SE2200-SEE with an average particle size of 0.5μm, and 2.2 parts of spherical silica YA050A-JGP with an average particle size of 50nm were added to a mixing tank, stirred evenly, and degassed under vacuum. The premixed material was then subjected to a three-roll milling and curing process to ensure full impregnation of the filler. The premixed material was then mixed with 20 parts of liquid aromatic amine curing agent ETHACURE. 100 are sequentially added to a mixing vessel, stirred evenly, and then vacuumed to remove bubbles, thus obtaining the chip-level underfill adhesive suitable for large-size chip packaging of the present invention.

[0045] Comparative Example 1

[0046] Preparation of chip-level underfill adhesive:

[0047] At room temperature, by weight, 20 parts of bisphenol F type epoxy resin YDF8170, 20 parts of aminophenol type epoxy resin JER630, 20 parts of bisphenol A type epoxy resin 850CRP, 3 parts of aminopropyltriethoxysilane, 2 parts of black paste, 40 parts of spherical silica SE5050-SEJ with an average particle size of 1.5μm, 7.8 parts of spherical silica SE2200-SEE with an average particle size of 0.5μm, and 2.2 parts of spherical silica YA050A-JGP with an average particle size of 50nm were added to a mixing tank, stirred evenly, and degassed under vacuum. Subsequently, the above premix was subjected to a three-roll mill process and a curing process to ensure full impregnation of the filler. The above premix and 20 parts of liquid aromatic amine curing agent ETHACURE 100 were added to a mixing tank in sequence, stirred evenly, and degassed under vacuum to obtain chip-level bottom filler.

[0048] Comparative Example 2

[0049] Preparation of chip-level underfill adhesive:

[0050] At room temperature, by weight, the following components are used: 20 parts of bisphenol F type epoxy resin YDF8170, 10 parts of aminophenol type epoxy resin JER630, 20 parts of bisphenol A type epoxy resin 850CRP, 10 parts of naphthalene type epoxy resin HP4032D, 3 parts of aminopropyltriethoxysilane, 2 parts of black paste, 40 parts of spherical silica SE5050-SEJ with an average particle size of 1.5 μm, 7.8 parts of spherical silica SE2200-SEE with an average particle size of 0.5 μm, and 50 nm spherical silica YA050A-JGP. 2.2 parts were added to a mixing tank, stirred evenly, and degassed under vacuum. The premixed material was then subjected to a three-roll milling process and a curing process to ensure full impregnation of the filler. The premixed material and 20 parts of liquid aromatic amine curing agent ETHACURE100 were added to a mixing tank in sequence, stirred evenly, and degassed under vacuum to obtain chip-level bottom filler.

[0051] test

[0052] The performance of the chip-level underfill adhesives of the present invention in Examples 1-5 and Comparative Examples 1-2 was tested through the following experiments.

[0053] High temperature modulus test at 1220℃

[0054] The high temperature modulus at 220℃ was obtained through DMA testing, using a single cantilever measurement mode, heating from -50℃ to 260℃ at a rate of 2℃ / min, with an oscillation frequency of 1Hz and an amplitude of 7.5μm.

[0055] Test 2 Flow Performance Test

[0056] The PCB board and silicon wafer are connected by solder balls with a diameter of 0.12mm, a center-to-center spacing of 0.8mm, and a height of 0.12mm. The flow performance of a large-size chip package at 100°C is simulated, and the flow time is recorded.

[0057] Thrust test at 260°C after 3Uhast 96h

[0058] The thrust at 260°C after 96 hours of Uhast testing was obtained by a push-pull tester. The adhesive was cured and bonded to the bare silicon wafer using a specific mold. After being placed in the Uhast chamber for 96 hours, the wafer was placed on a platform and heated at 260°C for 5 minutes before the thrust test was conducted at a rate of 50 mm / min.

[0059] Test 4: Coefficient of thermal expansion test (CTE1) <Tg)

[0060] The coefficient of thermal expansion was obtained through TMA testing, with a heating rate of 5°C / min from -20°C to 230°C, and the unit is ppm / °C. Tested according to ASTM D696.

[0061] Test 5K 1C test

[0062] K 1C The test was conducted according to the ASTM D5045 test standard, using the single-sided notch bending technique of a universal testing machine. A 3-point bending fixture was used, and the sample was tested at a crosshead speed of 10 mm / min.

[0063] The results of tests 1-5 are shown in Table 1.

[0064] Table 1. Comparison of test performance between samples of Examples 1-5 and Comparative Examples 1-2

[0065]

[0066] As can be seen from the data in Table 1, the chip-level underfill adhesive of the present invention has excellent flow properties, which can meet the operational requirements of large-size chip packaging; at the same time, it has low CTE, which effectively ensures the reliability of large-size chip packaging; the chip-level underfill adhesive of the present invention has excellent modulus and toughness, which solves the problem that traditional chip-level underfill adhesives are prone to cracking under thermal shock in large-size chip packaging; the product of the present invention, after curing and bonding with silicon wafers, still has high thrust strength to silicon wafers after being placed in a Uhast environmental chamber for 96 hours at 260°C, which makes large-size chip packaging have excellent reliability in high temperature and high humidity environments.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A chip-level underfill adhesive suitable for large-size chip packaging, comprising the following components by weight: 5-10 parts of self-synthesized multifunctional epoxy resin, 40-50 parts of epoxy resin, 3-6 parts of coupling agent, 2-4 parts of black paste, 50-70 parts of filler, and 20-30 parts of curing agent. The epoxy resin is one or a mixture of two or more of the following: aminophenol type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and naphthalene type epoxy resin. The structural formula of the self-synthesized multifunctional epoxy resin is: 。 2. The chip-level underfill adhesive suitable for large-size chip packaging according to claim 1, characterized in that, The self-synthesized multifunctional epoxy resin is prepared from the following raw materials: 30-40 parts of bisphenol compounds with aromatic imines, 5-10 parts of benzyltriethylammonium chloride, 180-220 parts of epichlorohydrin, and 25-30 parts of sodium hydroxide solution.

3. The chip-level underfill adhesive suitable for large-size chip packaging according to claim 2, characterized in that... The aromatic imine bisphenol compound is prepared from 25-30 parts of vanillin-based imine compound, 10-12 parts of aromatic aldehyde bisphenol compound, and 35-55 parts of ethanol; the vanillin-based imine compound is prepared from 22-25 parts of diaminomethylcyclohexane, 7-8 parts of vanillin, and 20-25 parts of ethanol; the aromatic aldehyde bisphenol compound is prepared from 8-10 parts of 4,4'-oxadiol, 650-750 parts of trifluoroacetic acid, 35-40 parts of hexamethylenetetramine, and 1000-1200 parts of hydrochloric acid.

4. The chip-level underfill adhesive suitable for large-size chip packaging according to claim 1, characterized in that, The synthesis route of the self-synthesized multifunctional epoxy resin is as follows: 。 5. The chip-level underfill adhesive for large-size chip packaging according to claim 1, characterized in that, The coupling agent is a silane coupling agent, specifically one or a mixture of two or more of 3-(2,3-epoxypropoxy)propylmethyldiethoxysilane, aminopropyltriethoxysilane, and phenylaminopropyltrimethoxysilane; the black paste is a premix of carbon black and epoxy resin in a ratio of 2:8; and the curing agent is a liquid aromatic amine curing agent.

6. The chip-level underfill adhesive for large-size chip packaging according to claim 1, characterized in that, The filler is a composition of spherical silica with different particle sizes; specifically, it is 15-25 spherical silica with an average particle size of 1.5µm: 2.7-5.2 spherical silica with an average particle size of 0.5µm: 0.5-1.5 spherical silica with an average particle size of 50nm; the surface of the spherical silica is epoxidized.

7. A chip-level underfill adhesive as described in any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: Add 8-10 parts of 4,4'-oxadiol and 650-750 parts of trifluoroacetic acid to a round-bottom flask and stir. Then slowly add 35-40 parts of hexamethylenetetramine to the mixture and stir at 90°C for 24 hours under an argon atmosphere. Then slowly cool the resulting mixture to room temperature and add 1000-1200 parts of hydrochloric acid and stir for 24 hours. Then extract the resulting mixture with dichloromethane, and wash the dichloromethane three times with deionized water and once with brine to remove water-soluble impurities. The organic phase was then dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation. Finally, the solvent was completely removed in a vacuum oven at 120°C to obtain purified bisphenol compounds with aromatic aldehydes. Add 22-25 parts of diaminomethylcyclohexane to a round-bottom flask; then, dissolve 7-8 parts of vanillin in 20-25 parts of ethanol, add the solution to the diaminomethylcyclohexane under nitrogen purging, and stir; then reflux the resulting mixture at 50°C for 3 hours, cool to room temperature, and remove the solvent and unreacted diaminomethylcyclohexane from the reactants by vacuum drying; purify the remaining product using a single-solvent recrystallization process with ethyl acetate to obtain vanillin-based imine compounds; Add 25-30 parts of the vanillin-based imine compound prepared above to a round-bottom flask; then, dissolve 10-12 parts of the aromatic aldehyde bisphenol compound prepared above in 35-55 parts of ethanol, add the solution to the round-bottom flask under nitrogen purging, and stir; then reflux the resulting mixture at 60°C for 3 hours, cool to room temperature, and remove the solvent from the reactants by vacuum drying; then purify the remaining product using a single-solvent recrystallization process with ethyl acetate to obtain the aromatic imine bisphenol compound; Add 30-40 parts of the bisphenol compound with aromatic imine prepared above, 2.5-5 parts of benzyltriethylammonium chloride, and 180-220 parts of epichlorohydrin to a three-necked flask, and stir at 80°C for 5 hours; cool to room temperature, add equal amounts of benzyltriethylammonium chloride and 25-30 parts of sodium hydroxide solution to the mixture, and continue stirring at room temperature for 8 hours; then extract the product three times with ethyl acetate, wash the obtained ethyl acetate phase three times with deionized water and brine, and then dry with anhydrous magnesium sulfate; concentrate the product by filtration and evaporation. The concentrated product was separated and purified by silica gel chromatography to prepare a self-synthesized multifunctional epoxy resin. (2) Add 5-10 parts of the self-synthesized multifunctional epoxy resin, 40-50 parts of epoxy resin, 3-6 parts of coupling agent, 2-4 parts of black paste and 50-70 parts of filler to a mixing tank, stir evenly, and degas under vacuum; then subject the above premix to a three-roll process and a curing process to ensure full impregnation of the filler; add the fully impregnated premix and 20-30 parts of curing agent to a mixing tank, stir evenly, and degas under vacuum to obtain chip-level bottom filler.

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