Low-alpha silicon fume / benzocyclobutene core chip package composite

Abstract

The application discloses a Low-alpha silicon powder / benzocyclobutene chip packaging composite material, which comprises 55-60wt% of phosphonate-benzocyclobutene resin matrix, 35-40wt% of filler system and 3-5wt% of bismaleimide synergistic additive; the phosphonate-benzocyclobutene resin matrix is obtained through ring-opening metathesis polymerization of norbornene phosphonate imidazole monomer and co-curing of benzocyclobutene monomer; the filler system contains epoxy silane modified double-particle-size Low-alpha silicon powder and aluminum hypophosphite modified nano Mg(OH)2; the alpha emissivity of the epoxy silane modified double-particle-size Low-alpha silicon powder is <0.001 cph / (cm 2 ·h), U≤0.1ppm, Th≤0.2ppm. The dielectric constant of the obtained chip packaging composite material is ≤2.45@77GHz, the dielectric loss is <0.0016, and the interfacial bonding strength is ≥7.2MPa, so that the chip packaging composite material is suitable for vehicle 77GHz millimeter wave radar packaging and meets the requirements of high frequency, radiation resistance and high reliability.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor packaging materials technology, specifically relating to a Low-α silicon micropowder / benzocyclobutene chip packaging composite material. Technical Background

[0002] As semiconductor technology rapidly advances towards high-density integration, high-frequency operation, and high reliability, chip packaging materials, as the core carrier connecting chips and external circuits, have become a key bottleneck restricting the upgrading of electronic devices. Applications such as RF chips for 5G communication base stations, AI computing chips, and radiation-resistant electronic devices in the aerospace field all place common high-performance demands on packaging materials across various scenarios: they must simultaneously possess ultra-low dielectric constant (Dk≤2.5@10GHz) and dielectric loss (Df<0.0020) to reduce high-frequency signal transmission loss; high glass transition temperature and thermal stability to withstand the high heat generated during chip operation; strong interfacial bonding strength to resist extreme environmental stresses such as temperature cycling and vibration, while also meeting processability requirements such as low warpage and high fill power.

[0003] Among current mainstream packaging materials, Low-α silicon micropowder can reduce α-ray emissivity and optimize thermal performance, but its surface hydroxyl activity is low, resulting in poor compatibility with organic resin interfaces. Direct filling easily leads to defects, causing increased dielectric loss and insufficient interface strength, which can exacerbate signal attenuation in high-frequency chips. BCB resin has ultra-low dielectric constant (Dk = 2.4~2.7), low dielectric loss (Df = 0.0005), and high heat resistance (Tg > 350℃), making it a preferred resin matrix for high-frequency and high-temperature applications. However, the pure system lacks π-electron delocalization structures, resulting in weak α-ray shielding and insufficient radiation resistance, which can easily lead to "soft errors" in chips in radiation environments such as nuclear industry and aerospace. Furthermore, its simple cross-linking network and poor mechanical toughness make it prone to embrittlement and cracking under wide temperature cycling conditions of -55 to 150℃, failing to meet the requirements of wide temperature applications such as automotive and aerospace.

[0004] Therefore, developing a Low-α silicon micropowder / BCB composite system that can synergistically control dielectric properties, radiation resistance, and interfacial bonding has become a key technological requirement in the field of high-end chip packaging. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a Low-α silicon micropowder / benzocyclobutene chip packaging composite material.

[0006] This invention provides a Low-α silicon micropowder / benzocyclobutene chip packaging composite material, comprising the following components in the following mass ratio:

[0007] Phosphonate-benzocyclobutene resin matrix: 55-60 wt%, obtained by ring-opening metathesis polymerization of norbornene phosphonate imidazole monomer and co-curing process with benzocyclobutene monomer; its structure is shown in formula (I):

[0008]

[0009] Filler system: 35-40 wt%, comprising epoxy silane-modified dual-particle size Low-α silica powder and aluminum phosphinate-modified nano-Mg(OH)₂ in a mass ratio of 9-15; the α emissivity of the epoxy silane-modified dual-particle size Low-α silica powder is <0.001 cph / (cm²). 2 ·h), U≤0.1ppm, Th≤0.2ppm;

[0010] Synergistic additive: 3-5 wt%, bismaleimide (BMI);

[0011] The norbornene phosphonate imidazole monomer is obtained by condensing o-phenylenediamine with 5-norbornene-2-acyl chloride to form a benzimidazole bridged ring intermediate, and then nucleophilically substituting it with diethyl bromofluoromethylphosphonate to achieve a phosphonate grafting process.

[0012] As a further embodiment of the present invention, the dual-particle-size Low-α silica powder is a mixture of powders with an average particle size of 10-15 μm and powders with an average particle size of 2-5 μm, in a mass ratio of (13-15):(5-0.7); the nano-Mg(OH)2 has an average particle size of 30-50 nm.

[0013] As a further aspect of the present invention, the composite material is prepared by a method comprising:

[0014] S1. Preparation of dual-particle-size modified Low-α silica powder: Prepare an ethanol-water solution containing epoxy silane at a water-silicon molar ratio of 6-10:1, and add isopropanol as a solubilizer, and pre-hydrolyze for 15-30 min; separately prepare an aqueous dispersion of plasma-activated dual-particle-size Low-α silica powder, mix it with the silane solution; hydrolyze under pulsed microwave assistance at 40℃ for 1-2 h to obtain dual-particle-size modified Low-α silica powder;

[0015] S2. Preparation of aluminum hypophosphite-modified nano-Mg(OH)2: Add aluminum hypophosphite to an ethanol-water solution of nano-Mg(OH)2; add silane coupling agent dropwise under constant temperature stirring at 60-70℃ and react for 2-3 hours; filter and vacuum dry to obtain modified nano-Mg(OH)2.

[0016] S3, Resin matrix copolymerization: Under N2 atmosphere, norbornene phosphonate imidazole monomer is dissolved in cyclopentyl methyl ether; in the presence of Grubbs catalyst, ring-opening metathesis polymerization is carried out at 60-80℃ for 2-3 hours to form a prepolymer, and an inhibitor is added to quench the polymerization after completion.

[0017] Grubbs catalyst was separated, and benzocyclobutene monomer and tris(pentafluorophenyl)borane (B(C6F5)3) were added. The temperature was raised to 180°C at a rate of 1-3°C / min and held for 1-2 hours to initiate the ring-opening of benzocyclobutene. The temperature was then raised to 200-220°C and held for 1-2 hours to cure, yielding phosphonate-benzocyclobutene resin matrix.

[0018] The molar ratio of the benzocyclobutene monomer to the norbornene phosphonate imidazole monomer is 0.6–0.7.

[0019] S4. Composite molding: Add dual-size modified Low-α silica powder, aluminum phosphinate modified nano-Mg(OH)2 and bismaleimide to the phosphonate-benzocyclobutene resin matrix of S3, shear dispersion and vacuum degassing; then perform stepwise thermosetting at 120-180℃ to obtain the encapsulated composite material.

[0020] In step S1, the epoxy silane molecules used for modification contain hydrophobic epoxycyclohexyl groups. When directly dissolved in a high-water-volume ethanol aqueous solution, they are prone to self-polymerization due to excessively high local concentrations, forming a colloidal suspension. The silanols generated by the hydrolysis of epoxy silanes in water are highly reactive. If the water-silicon molar ratio is too high, the risk of hydrolysis and self-polymerization increases, which may lead to the failure of the modifier. Therefore, it is necessary to strictly control the water content and the water-silicon molar ratio.

[0021] As a further embodiment of the present invention, in step S1: the amount of isopropanol is 3-6 wt%, and the mass of epoxy silane is 8-15 wt% of the dual-particle-size Low-α silica powder;

[0022] The plasma activation parameters are: 100-200W power for 3-5 minutes, and the pulse hydrolysis parameters are: power 300-500W, duty cycle 45-50%.

[0023] As a further embodiment of the present invention, in step S1: the epoxy silane is a silane coupling agent containing at least one epoxy group, selected from at least one of (2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (CAS: 3388-04-3), 5,6-epoxyhexyltriethoxysilane (CAS: 86138-01-4), tris(epoxypropoxypropyldimethylsiloxy)phenylsilane (CAS: 90393-83-2), methyl-terminated silicone oil (CAS: 67762-95-2), ethoxydimethyl[3-(epoxyethoxy)propyl]silane (CAS: 17963-04-1), 3-glycidyl etheroxypropyltriethoxysilane (CAS: 2602-34-8), or 1,3-bis[2-(3,4-epoxycyclohexyl)ethyl]tetramethyldisiloxane (CAS: 18724-32-8).

[0024] As a further embodiment of the present invention, in step S2: the aluminum phosphite is selected from phenyl aluminum phosphite or diethyl aluminum phosphite, and the amount added is 3 to 8 wt% of the mass of nano Mg(OH)2; the silane coupling agent is 3-aminopropyltriethoxysilane, and the amount used is 0.5 to 1.0 wt% of the mass of nano Mg(OH)2.

[0025] Aluminum phosphonate-modified nano-magnesium hydroxide introduces Al 3+ It can chelate with the hydroxyl groups on the surface of nano-Mg(OH)2 to form Al-O-Mg bonds to enhance interfacial bonding: the reaction of phosphonic acid groups with the epoxy groups on the surface of dual-particle-size modified Low-α silica micropowder and the hydrogen bonding with the phosphonate monomers of the copolymer resin can synergistically improve the interfacial bonding strength.

[0026] Ring-opening metathesis polymerization refers to the ring-opening polymerization reaction of cyclic olefins. In step S3, the norbornene group in the norbornene phosphonate imidazole monomer undergoes ring-opening metathesis polymerization under the action of Grubbs catalyst, forming a polymer backbone while retaining the double bonds; benzocyclobutene undergoes thermal ring-opening polymerization at >200℃ to form a highly reactive conjugated diene intermediate (o-quinolone dimethane), which participates in the Diels-Alder process with the norbornene phosphate imidazole metathesis polymerization product, forming a phosphonate-benzocyclobutene resin polymer. Due to the large steric hindrance of the norbornene phosphonate monomer, if the BCB ratio is too high, it is easy to cause self-polymerization side reactions and uneven cross-linking network, resulting in high brittleness and increased dielectric loss. If the BCB ratio is too low, the degree of cross-linking will be insufficient, and the hygrothermal stability will deteriorate.

[0027] As a further embodiment of the present invention, in step S3: the Grubbs catalyst is dichloro[1,3-bis(2-methylphenyl)-2-imidazolidinedimethyl](2-isopropoxybenzylmethyl)ruthenium(II), and the amount used is 0.8-1.2 mol% of the molar amount of norbornene phosphonate imidazolium; the polymerization inhibitor is 2,6-di-tert-butyl-4-methylphenol (BHT) or 4-methoxyphenol (MEHQ), and the amount used is 0.1-0.12 wt% of the total mass of the system; the amount of tris(pentafluorophenyl)borane is 1.5-2.0 wt% of the mass of benzocyclobutene.

[0028] As a further embodiment of the present invention, in step S4: the vacuum degassing conditions are: -0.09MPa, degassing at 80℃ for 1h; the step-by-step curing is: maintaining a heating rate of 2-3℃ / min, curing at 120℃ and 150℃ for 1h respectively, and finally curing at 180℃ for 2h.

[0029] As a further embodiment of the present invention, the dielectric constant of the composite material is ≤2.45@77GHz, the dielectric loss is <0.0016, and the interfacial bonding strength is ≥7.2MPa.

[0030] Beneficial effects:

[0031] 1. Excellent dielectric properties: The encapsulation composite material provided by this invention has a dielectric constant ≤2.45@77GHz, a dielectric loss <0.0016, and a signal insertion loss ≤0.16dB / mm at 77GHz high frequency, which can meet the requirements of low signal attenuation in high-frequency communication and solve the problem of the surge in dielectric loss of traditional materials at high frequencies.

[0032] 2. Low alpha emission: The dual-particle-size modified Low-alpha silicon micropowder modified with epoxy silane has a high grafting density. The silane layer and the Si-OH on the surface of the silicon micropowder condense to form a dense hydrophobic layer, which seals the adsorption sites of radioactive nuclides and physically blocks the escape of alpha particles. In addition, the delocalized π electrons of the benzimidazole ring in the norbornene phosphonate imidazole monomer absorb the kinetic energy of alpha particles, converting radioactive decay into harmless thermal energy and reducing the risk of "soft errors" in the chip.

[0033] 3. Enhanced interfacial bonding and mechanical properties: The synergistic effect of epoxy silane-modified dual-particle-size Low-α silica powder and alkyl phosphinate-aluminate-modified nano-Mg(OH)2 reduces the agglomeration tendency of the filler system, ensures uniform dispersion during the composite molding process, and achieves an interfacial bonding strength of ≥7.2MPa for the composite material.

[0034] 4. Excellent reliability: Warpage deformation is controlled by a stepped curing process, and the water absorption rate after humid heat aging is ≤0.012%, which significantly improves reliability; the vacuum degassing process effectively avoids pore defects and is suitable for large-scale production of high-density chip packaging. Attached Figure Description

[0035] Figure 1 The 1H NMR spectrum of the norbornene phosphonate imidazole monomer obtained in the preparation example.

[0036] Figure 2 A schematic diagram of the formation of the phosphonate-benzocyclobutene resin matrix in Example 1.

[0037] Figure 3 Infrared absorption spectra of the packaging materials of Example 1 and Comparative Examples 1-4. Detailed Implementation

[0038] To more fully demonstrate the practical applications and technical advantages of the present invention, the following detailed description is provided through multiple embodiments and comparative examples. Those skilled in the art should understand that these embodiments are merely examples and do not constitute a limitation on the scope of protection of the present invention.

[0039] Unless otherwise specified, the experimental methods used in the specific implementation methods are all conventional methods; the materials and reagents used are all commercially available unless otherwise specified.

[0040] The properties and sources of some raw materials used in the examples and comparative examples are as follows:

[0041] Bismaleimide (BMI), 96% purity, Beijing Innocare Technology Co., Ltd.

[0042] 5-Norbornene-2-acyl chloride, 97% purity, Shanghai Bide Pharmaceutical Technology Co., Ltd.;

[0043] Diethyl bromofluoromethylphosphonate, 97% purity; Tris(epoxypropoxypropyldimethylsiloxy)phenylsilane, 95% purity, Beijing Bailingwei Technology Co., Ltd.

[0044] Aluminum phenylphosphite, 99% purity, Wuhan Xingzhongcheng Technology Co., Ltd.

[0045] 4-Dimethylaminopyridine (DMAP), 99% purity, Shanghai Kaisai Chemical Co., Ltd.; Benzocyclobutene (BCB), 97% purity; Cyclopentyl methyl ether (CPME, anhydrous grade), 99.5% purity, Shanghai Maclean Biochemical Technology Co., Ltd.

[0046] o-Phenylenediamine, 98% purity; 3-aminopropyltriethoxysilane (KH550), 98% purity; 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 97% purity; 2,6-di-tert-butyl-4-methylphenol (BHT), AR, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0047] Grubbs C627, namely dichloro[1,3-bis(2-methylphenyl)-2-imidazolidinedimethyl](2-isopropoxybenzylmethyl)ruthenium(II), 97% purity; tris(pentafluorophenyl)boron, 95% purity, Sigma-Aldrich (Shanghai) Trading Co., Ltd.

[0048] GE-0035 and GE-0100 silicon micropowders have D50 values ​​of 3.5μm and 12μm, respectively; whiteness 94; moisture content ≤0.2wt%; silica content >99.5wt%; Fe2O3 ≤100ppm; magnetic material ≤10ppm; density 2.2g / cm³. 3 Dielectric constant (Dk) = 3.68, dielectric loss (Df) = 0.00015, purchased from Guangdong Haike New Materials Technology Co., Ltd.

[0049] Before modification, all silicon micropowders underwent plasma pretreatment to remove surface organic impurities and increase hydroxyl density. The pretreatment process was as follows: the silicon micropowder was placed in a radio frequency plasma reactor. Argon gas was introduced, and the treatment was carried out for 5 minutes under a vacuum of 50 Pa and a power of 100 W.

[0050] VK-MHT01 model nano Mg(OH)2, purity 99.9%, average particle size 35nm, Fe content ≤0.003wt%, Cu content ≤0.003wt%, specific surface area 55m². 2 / g, purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0051] Preparation Example

[0052] The norbornenephosphonate imidazole monomer was synthesized via the following route:

[0053]

[0054] 1) Synthesis of benzimidazole intermediate 1:

[0055] In a 500 mL three-necked flask, o-phenylenediamine (10.8 g, 0.1 mol) was dissolved in 100 mL of anhydrous o-dichlorobenzene with stirring. Pyridine (0.3 mol) and DMAP (0.01 mol) were added. Under nitrogen protection, the mixture was placed in an ice-water bath at 0–5 °C. 5-norbornene-2-acyl chloride (CAS: 27063-48-5) was slowly added dropwise using a constant-pressure dropping funnel at a rate of 0.5 drops / s to avoid hydrolysis of the acyl chloride and local overheating. After the addition was complete, the ice-water bath was removed, the temperature was raised to 40 °C, and the reaction was stirred for 6 h (TLC monitoring showed that the starting material disappeared, the developing solvent was petroleum ether: ethyl acetate = 2:1, the starting material point Rf≈0.3, and the intermediate point Rf≈0.6). The temperature was then raised to 150 °C and refluxed for 3 h, resulting in intramolecular cyclization to form a benzimidazole skeleton (TLC showed that the starting material point completely disappeared, and a single new point was formed Rf≈0.7).

[0056] After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was slowly poured into 200 mL of deionized water (to quench unreacted acyl chlorides). The mixture was stirred for 30 min and allowed to stand to separate into layers. The liquid was separated, and the organic phase was washed with 5 wt% NaHCO3 solution (2 × 50 mL) to remove residual HCl and triethylamine salt. The mixture was washed with water until neutral, dried over anhydrous MgSO4, and filtered. The crude product was obtained by vacuum distillation. It was dissolved in ethanol (80 mL) under reflux, filtered while hot, and the filtrate was cooled to 0 °C to crystallize. The crystals were then filtered to obtain white needle-like crystalline intermediate 1. Yield: 88%. Purity: >98%.

[0057] 2) Synthesis of norbornene phosphonate imidazole monomer;

[0058] Intermediate 1 (0.1 mol) and Cs₂CO₃ (0.05 mol) were added to 100 mL of DMF and stirred at 60 °C for 30 min under nitrogen protection. Diethyl bromofluoromethylphosphonate (CAS: 65094-22-6, 0.1 mol) was added dropwise, and the mixture was reacted at 50 °C for 6 h (TLC monitoring, developing solvent: petroleum ether / ethyl acetate = 3:1). Cs₂CO₃ was removed by filtration, and DMF was removed by vacuum distillation. The residue was extracted with 150 mL of water and ethyl acetate (3 × 50 mL). The organic phase was dried over anhydrous magnesium sulfate and purified by column chromatography to obtain the product (Mw = 396.37 g / mol), with a yield of 82%. Its 1H NMR (CDCl₃, 400 MHz) results are shown below. Figure 1 .

[0059] Example 1

[0060] A Low-α silicon micropowder / BCB chip encapsulation composite material comprises: 60 wt% resin matrix, 35 wt% filler system (dual-particle-size modified Low-α silicon micropowder: aluminum phosphinate modified nano-Mg(OH)2 in a mass ratio of 12:1), and 5 wt% BMI. The specific preparation process is as follows:

[0061] S1. Preparation of dual-particle-size modified Low-α silica powder:

[0062] 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (2.0 g) was dissolved in ethanol-water (7.83 g anhydrous ethanol + 1.17 g water), and isopropanol (3.2 g) was added to aid dissolution, resulting in a silane pre-hydrolyzed solution. The pH of the solution was adjusted to 4.0 with acetic acid, and the solution was pre-hydrolyzed at 60 °C for 30 min. Subsequently, plasma-treated low-α silica powder with two particle sizes (20 g, with a particle size ratio of 1.5:0.5) was dispersed in water (80 g) and mixed with the above silane pre-hydrolyzed solution to obtain a mixed modified solution. The solution was stirred for 1.5 h at 40 °C and 300 rpm using pulsed microwave (400 W, 2.45 GHz, duty cycle 50%). The solution was washed three times with ethanol, centrifuged (5000 rpm, 10 min), and vacuum dried at 40 °C.

[0063] The alpha particle emissivity was directly measured using an Inspector IA-V2 multi-functional X-ray detector (alpha detection efficiency 36% @ 5.5 MeV), with the background noise calibrated to 0.0001 cph / cm². 2 The cumulative measurement time was 1000 minutes.

[0064] Monitoring with an Agilent 7900 inductively coupled plasma mass spectrometer 238 U、 232 Th mass number, detection limits: 0.02 ppb (U), 0.03 ppb (Th).

[0065] The N1s / Si 2p peak area ratio before and after modification was determined by XPS to obtain the epoxy silane grafting density.

[0066] The test results are summarized in Table 1.

[0067] Table 1

[0068] performance Uranium (U) content Thorium (Th) content Alpha particle emissivity Epoxysilane grafting density result 0.05ppm 0.12ppm <![CDATA[0.0006cph / cm 2 ]]> <![CDATA[5.0 per nm 2 >

[0069] S2. Preparation of aluminum hypophosphite-modified Mg(OH)₂: A toluene solution containing 3g of nano-Mg(OH)₂ was added to an ethanol-water solution (v:v = 3:1) and ultrasonically dispersed until homogeneous. The pH of the solution was adjusted to approximately 4.0. 0.18g of phenyl aluminum hypophosphite was added, and the mixture was heated to 65℃ while stirring. Subsequently, 0.024g of KH₅₅O was added, and the mixture was stirred at 65℃ for 3 hours. After centrifugation and washing, the mixture was vacuum dried at 70℃ for 6 hours. The zeta potential measured by DLS was -49mV, and the water contact angle measured by a surface goniometer was 110°.

[0070] S3, resin matrix, according to Figure 2 The path shown is synthesized as follows:

[0071] In a dry Schlenk tube, 33 g (78.2 mmol) of norbornene phosphonate imidazole monomer obtained in Example 1 was dissolved in CPME (99 g); the reactor was evacuated to 0.1 mbar and purged with nitrogen three times to maintain O2 < 10 ppm. Then, a solution of dichloro[1,3-bis(2-methylphenyl)-2-imidazolidinedimethyl](2-isopropoxybenzylmethyl)ruthenium(II) (0.767 mmol)-tetrahydrofuran was injected. The system was heated to 70 °C and stirred for 3 h (the characteristic peak of norbornene was monitored by FT-IR at ~1650 cm⁻¹). -1 (Disappeared); Cool the system to 50℃ and add 0.036g BHT. Stir with 5% EDTA disodium salt solution for 1h to precipitate Ru-EDTA complex, then filter;

[0072] The filtrate was poured back into a Schlenk tube and heated to 80°C under a nitrogen atmosphere. BCB monomer (5.8 g) and tris(pentafluorophenyl)boron (0.11 g) were added. The reaction system was heated to 180°C at a rate of 1°C / min and kept at that temperature for 1 h. Then the temperature was further increased to 220°C and kept at that temperature for 2 h to obtain the resin matrix.

[0073] The molecular weight of the liquid crystal copolymer was determined using a Waters 1515 gel permeation chromatography system (GPC, equipped with a Styragel HR4 / HR5 column). Test conditions: mobile phase was THF (flow rate 1 mL / min), column temperature 35 °C, injection volume 100 μL (sample concentration 1 mg / mL); a standard curve was plotted using polystyrene standards, and the number-average molecular weight (Mn) and dispersity (PDI = (Mw / Mn)) were calculated.

[0074] The GPC test result is: Mn=(3.82±0.06)×10 4 g / mol, PDI = 1.15 ± 0.02.

[0075] (4) Composite molding process: Dual-size modified Low-α silica powder (31.1g), aluminum phosphite modified Mg(OH)2 (3.9g) and BMI (5g) were added to the above resin matrix (60g) in three batches and sheared and dispersed at 2000rpm for 20min; the vacuum degree was set to -0.09MPa and vacuum degassing was carried out at 80℃ for 60min; finally, the temperature was increased at a rate of 2.5℃ / min to complete the step-by-step curing process: ring opening at 120℃×1h, crosslinking at 150℃×1h and densification at 180℃×2h to obtain the encapsulated composite material.

[0076] Example 2

[0077] The difference from Example 1 is: resin matrix 55wt%, filler system 40wt% (dual particle size modified Low-α silica powder: aluminum phosphinate modified nano Mg(OH)2 = 12:1), BMI 5wt%. The rest is the same as in Example 1.

[0078] Example 3

[0079] The difference from Example 1 is that in step S3, the molar ratio of BCB monomer to norbornenephosphonate imidazole monomer was adjusted to 4:1. The GPC test result of the resin matrix is: Mn = (6.26 ± 0.08) × 10 4 g / mol, PDI = 1.38 ± 0.04.

[0080] The rest is the same as in Example 1.

[0081] Example 4

[0082] The difference from Example 1 is that the water-silicon molar ratio in step S1 is adjusted to 6:1. The relevant properties of the dual-particle-size modified Low-α silica powder obtained in step S1 are shown in Table 2.

[0083] Table 2

[0084] performance Uranium (U) content Thorium (Th) content Alpha particle emissivity Epoxysilane grafting density result 0.01ppm 0.08ppm <![CDATA[0.0003cph / cm 2 ]]> <![CDATA[5.3 per nm 2 >

[0085] Examples 5-6

[0086] The difference from Example 1 is that, while keeping the amount of filler system the same, the mass ratio of dual-particle-size modified Low-α silica powder to aluminum phosphinate modified nano Mg(OH)2 is adjusted to 9:1 and 15:1, respectively.

[0087] Example 7

[0088] The difference from Example 1 is that the epoxy silane is replaced with tris(epoxypropoxypropyldimethylsiloxy)phenylsilane, while the amount and other processes are the same.

[0089] Comparative Example 1

[0090] The difference from Example 1 is that pure BCB polymerization was used in step S3. That is, the same amount of BCB and tris(pentafluorophenyl)boron as in Example 1 were dissolved in CPME in a Schlenk tube; under a nitrogen atmosphere, the reaction system was heated to 180°C at a rate of 1°C / min and held for 1 hour; then it was further heated to 220°C and held for 2 hours to obtain the BCB homopolymer resin matrix.

[0091] The GPC test result for the homopolymer resin matrix is: Mn=(2.85±0.12)×10 4 g / mol, PDI = 2.70 ± 0.1.

[0092] Everything else is the same as in Example 1.

[0093] Comparative Example 2

[0094] The difference from Example 1 is that the dual-particle-size Low-α silica powder used is not modified with epoxy silane.

[0095] Comparative Example 3

[0096] The difference from Example 1 is that the nano-Mg(OH)2 used is not modified with aluminum diisobutylphosphinate.

[0097] Comparative Example 4

[0098] The difference from Example 1 is that the molar ratio of BCB monomer to norbornene phosphonate imidazole monomer was adjusted to 1:1. The GPC test results of the resin matrix are: Mn = (2.21 ± 0.3) × 10⁻⁶. 4 g / mol, PDI = 3.01 ± 0.20.

[0099] The rest is the same as in Example 1.

[0100] Test Project

[0101] (1) Dielectric properties: Dielectric constant Dk@77GHz and dielectric loss / Df@77GHz were tested according to IPC TM-6502.5.5. The sample was cut into 50mm×50mm×0.5mm thin sheets, and the surface was polished with sandpaper until Ra≤0.2μm. The sample was pre-baked at 120℃ for 2 hours to remove moisture before testing. Automatic scanning was initiated at an ambient temperature of 23℃±1℃ and humidity of 50%±5%, displaying the dielectric constant and dielectric loss factor curves in real time. The process was stopped immediately upon the appearance of an electric arc, and the sample flatness was checked.

[0102] (2) Alpha ray shielding efficiency: The test standard is ISO 18589. An ORTEC alpha spectrometer (equipped with a PIPS detector) was used, and the alpha source was... 241 Am standard source (activity 100 kBq, energy 5.486 MeV). The sample was fixed between the source and the detector (distance 2 cm). Background count was measured for 30 min, sample count for 3600 s, and shielding efficiency was calculated as (1 - sample count / background count) × 100%.

[0103] (3) Thermal properties: The thermal conductivity of the material was measured using the laser flash method (LFA) according to the ASTM E1461 test standard. The test temperature was 25℃, and the test was repeated 3 times and the average value was taken. A DSC 2500 differential scanning calorimeter was used for testing, referring to the ASTM D3418 standard. The sample was quenched in liquid nitrogen and then ground into powder. The test conditions were as follows: flow rate 50 mL / min, heating rate 10℃ / min; temperature range 25~500℃; the inflection point temperature of the second heating curve was taken as the Tg value.

[0104] (4) Interface strength test. The specimen was cut into Type 1BA dumbbell-shaped specimens (150mm long, 25mm gauge length, 10mm width) and mounted on a universal testing machine (model INSTRON 5967, load cell 5kN), ensuring secure clamping. Following ISO 527 standards, under environmental conditions of 23℃ and 50% humidity, a tensile force was applied to the specimen at a tensile rate of 1mm / min. The tensile strength and tensile modulus were measured to obtain the interfacial bond strength.

[0105] (5) Damp heat aging test: Aging test at 85℃ / 85%RH. The sample was placed in a damp heat environment chamber (ESPECSH-241 constant temperature and humidity chamber), with the temperature set at 85℃ and relative humidity at 85%, for 1000 hours of aging treatment. The initial mass was weighed using an analytical balance (accuracy 0.1mg). After aging, the surface was wiped with anhydrous ethanol, vacuum dried at 60℃ for 2 hours, and weighed again. The change in water absorption rate of the sample was detected. Water absorption rate = (mass after aging - initial mass) / initial mass × 100%.

[0106] (6) Thermal cycling test: Place the sample in a Thermotron SE-16 high and low temperature shock chamber and set the cycling parameters according to JESD22-A104 standard: -55℃ (hold for 30 min), 125℃ (hold for 30 min), with a transition time of <10 s; after 1000 cycles, check whether the sample shows delamination or cracking defects. Delamination area ratio = delamination area / total sample area × 100%, where the delamination area refers to the area with continuous gaps >5 μm.

[0107] The relevant performance test results of the examples and comparative examples are summarized in Table 3.

[0108] Table 3

[0109]

[0110]

[0111] As shown in Table 1, the reduced proportion of resin matrix in Example 2 and the reduced proportion of phosphonate in the copolymer resin in Example 3 both resulted in weakened interfacial reinforcement, increased water absorption during humid heat aging, and a slightly higher delamination rate after thermal cycling. Furthermore, the increased proportion of BCB segments in the copolymer in Example 3 led to a rise in Tg to 355℃. This is because the increased crosslinking network density inhibits chain segment movement. In Example 4, the increased silane content compared to Example 1 resulted in higher grafting density, higher interfacial strength, and a denser interface that effectively blocked moisture, significantly reducing water absorption. In Example 5, when the proportion of aluminum phosphonate-modified nano-Mg(OH)2 in the filler system increased, the high surface energy of Mg(OH)2 made it prone to agglomeration and interfacial defects, increasing the water absorption rate to 0.010% and the delamination rate to 0.12%; however, Mg(OH)2 exhibited good thermal conductivity, resulting in improved thermal conductivity. Example 6 showed that an increased proportion of dual-particle-size modified Low-α silica powder effectively suppressed thermal expansion, leading to an increase in Tg.

[0112] Although Comparative Example 1 had the highest Tg, the lack of flexible segments in pure BCB resulted in insufficient interfacial strength and decreased thermal cycling stability. Furthermore, the absence of low-polarity modulation from benzimidazole cyclic phosphonate led to an increase in dielectric constant. In Comparative Example 4, the copolymer resin had an excessive proportion of norbornene phosphonate imidazole monomer, which increased its polarity, raising Df to 0.0032. Simultaneously, Tg plummeted to 290℃, the water absorption rate during wet heat aging increased to 0.09%, and the delamination rate after thermal cycling increased to 6.8%.

[0113] In Comparative Example 2, the low-α silica micropowder with dual particle size was not treated with silane, resulting in decreased interfacial bonding and interfacial strength. Simultaneously, interfacial defects led to moisture ingress, increasing water absorption and delamination rate after thermal cycling. Poor filler dispersion resulted in low thermal conductivity. Dielectric constant and loss increased. In Comparative Example 3, the nano-Mg(OH)2 lacked aluminum hypophosphite modification, thus increasing the dielectric loss of the encapsulation material and decreasing interfacial bonding strength.

[0114] Furthermore, the encapsulation materials of Example 1 and Comparative Examples 1-4 were tested using Fourier transform infrared spectroscopy (FTIR) with an IZ-10 diffuse infrared reflectometer (IR, Thermo Fisher Scientific, USA). Wavenumbers ranged from 400 to 4000 cm⁻¹. -1 4cm resolution -1 The scan was performed 32 times, and the test mode was set to "Smart iTR diamondATR". Results are shown below. Figure 3 .

[0115] Example 1 at 2900cm -1 The region exhibits a moderate-intensity CH stretching vibration absorption peak, which is attributed to the octadecyl chain of the modified magnesium hydroxide. Comparative Example 1, lacking the phosphonate monomer, shows a significantly reduced absorption peak intensity. Example 1 shows an absorption peak intensity at 1580 cm⁻¹. -1 The peak at this location is attributed to the C=N stretching vibration of the imidazole ring. In Comparative Example 1, the peak disappears here due to the absence of the imidazole ring phosphonate monomer; in Comparative Example 4, the peak intensity decreases due to an imbalanced monomer ratio. Additionally, the peak intensity at approximately 1700 cm⁻¹ in Comparative Example 1... -1 The presence of a strong carbonyl (C=O) absorption peak nearby also indicates the formation of byproducts from the oxidation of carboxylic acids. Comparative Example 2 shows an absorption peak at 3400 cm⁻¹. -1 The absorption peak in the nearby OH / NH stretching vibration region is significantly higher, indicating that there are hydroxyl groups or adsorbed water on the surface of the untreated, dual-particle-size Low-α silica microparticles. In Comparative Example 3, the nano-Mg(OH)₂, without aluminum phosphonate modification, exhibits a peak at approximately 3690 cm⁻¹. -1 There is a sharp absorption peak of the Mg-OH group at that point.

[0116] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A Low-α silicon micropowder / benzocyclobutene chip encapsulation composite material, characterized in that, The components include the following mass ratios: Phosphonate-benzocyclobutene resin matrix: 55~60wt%, obtained by ring-opening metathesis polymerization of norbornene phosphonate imidazole monomer and co-curing process of benzocyclobutene monomer; the molar ratio of benzocyclobutene monomer to norbornene phosphonate imidazole monomer is 0.6~0.7; the co-curing process includes the following steps: under N2 atmosphere, norbornene phosphonate imidazole is dissolved in cyclopentyl methyl ether; in the presence of Grubbs catalyst, ring-opening metathesis polymerization is carried out at 60~80℃ for 2~3h to form a prepolymer, and after completion, a polymerization inhibitor is added to quench; the Grubbs catalyst is separated, and benzocyclobutene and tris(pentafluorophenyl)borane are added; the system is further heated to 180℃ at a rate of 1~3℃ / min under N2 atmosphere and held for 1~2h; then heated to 200~220℃ and held for curing for 1~2h to obtain phosphonate-benzocyclobutene resin matrix; The phosphonate-benzocyclobutene resin matrix, as determined by GPC, has a number-average molecular weight of (3.82±0.06)×10⁻⁶. 4 g / mol; Filler system: 35~40wt%, containing epoxy silane-modified dual-particle size Low-α silica micropowder and aluminum phosphinate-modified nano-Mg(OH)2 in a mass ratio of 9~15; the α emissivity of the epoxy silane-modified dual-particle size Low-α silica micropowder is <0.001cph / (cm). 2 ·h), U≤0.1ppm, Th≤0.2ppm; Synergistic additive: 3~5wt%, bismaleimide; The norbornene phosphonate imidazole monomer is obtained by condensing o-phenylenediamine with 5-norbornene-2-acyl chloride to form a benzimidazole bridged ring intermediate, and then nucleophilically substituting it with diethyl bromofluoromethylphosphonate to achieve a phosphonate grafting process.

2. The composite material according to claim 1, characterized in that, The dual-particle-size Low-α silica powder is a mixture of powders with an average particle size of 10~15μm and powders with an average particle size of 2~5μm, in a mass ratio of (13~15):(5~7); the nano-Mg(OH)2 has an average particle size of 30~50nm.

3. The composite material according to claim 1, characterized in that, Its preparation methods include: S1. Preparation of dual-particle-size modified Low-α silica powder: Prepare an ethanol-water solution containing epoxy silane at a water-silicon molar ratio of 6~10:1, and add isopropanol as a solubilizer, and pre-hydrolyze for 15~30 min; separately prepare a plasma-activated dual-particle-size Low-α silica powder-water dispersion, mix it with the silane solution; hydrolyze under pulsed microwave assistance at 40℃ for 1~2 h to obtain modified dual-particle-size Low-α silica powder; S2. Preparation of aluminum hypophosphite-modified nano-Mg(OH)2: Add aluminum hypophosphite to an ethanol-water solution of nano-Mg(OH)2; add silane coupling agent dropwise under constant temperature stirring at 60~70℃ and react for 2~3h; filter and vacuum dry to obtain modified nano-Mg(OH)2; S3, Resin matrix copolymerization: Under N2 atmosphere, norbornene phosphonate imidazole is dissolved in cyclopentyl methyl ether; in the presence of Grubbs catalyst, ring-opening metathesis polymerization is carried out at 60~80℃ for 2~3h to form a prepolymer, and an inhibitor is added to quench the polymerization after completion; Separate the Grubbs catalyst, add benzocyclobutene and tris(pentafluorophenyl)borane; continue to heat the system to 180℃ at a rate of 1~3℃ / min under N2 atmosphere, hold for 1~2h; then heat to 200~220℃, hold for 1~2h to cure, to obtain phosphonate-benzocyclobutene resin matrix. S4. Composite molding: Modified dual-particle-size Low-α silica micropowder, aluminum phosphite-modified nano Mg(OH)2 and bismaleimide are added to the phosphonate-benzocyclobutene resin matrix of S3, shear dispersion and vacuum degassing are performed; then the encapsulated composite material is obtained by step thermosetting at 120~180℃.

4. The composite material according to claim 3, characterized in that, In step S1: the mass of epoxy silane is 8~15 wt% of the dual-particle-size Low-α silica powder; The plasma activation parameters are: 100~200W power for 3~5 minutes, and the pulse hydrolysis parameters are: power 300~500W, duty cycle 45~50%.

5. The composite material as described in claim 3, characterized in that, In step S1: the epoxy silane is a silane coupling agent containing at least one epoxy group, selected from at least one of (2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 5,6-epoxyhexyltriethoxysilane, tris(epoxypropoxypropyldimethylsiloxy)phenylsilane, ethoxydimethyl[3-(epoxyethoxy)propyl]silane, 3-glycidyl etheroxypropyltriethoxysilane, or 1,3-bis[2-(3,4-epoxycyclohexyl)ethyl]tetramethyldisiloxane.

6. The composite material according to claim 3, characterized in that, In step S2: the aluminum phosphite is selected from aluminum phenylphosphite or aluminum diethylphosphite, and the amount added is 3 to 8 wt% of the mass of nano Mg(OH)2; the silane coupling agent is 3-aminopropyltriethoxysilane, and the amount used is 0.5 to 1.0 wt% of the mass of nano Mg(OH)2.

7. The composite material according to claim 3, characterized in that, In step S3: the Grubbs catalyst is dichloro[1,3-bis(2-methylphenyl)-2-imidazolidinedimethyl](2-isopropoxybenzyl)ruthenium(II), and the amount used is 0.8~1.2 mol% of the molar amount of norbornene phosphonate imidazolium; the polymerization inhibitor is 2,6-di-tert-butyl-4-methylphenol or 4-methoxyphenol, and the amount used is 0.1~0.12 wt% of the total mass of the system; the amount of tris(pentafluorophenyl)borane is 1.5~2.0 wt% of the mass of benzocyclobutene.

8. The composite material according to claim 3, characterized in that, In step S4: the vacuum degassing conditions are: -0.09MPa, degassing at 80℃ for 1h; the step-curing is: maintaining a heating rate of 2~3℃ / min, curing at 120℃ and 150℃ for 1h respectively, and finally curing at 180℃ for 2h.

9. The composite material according to claim 3, characterized in that, The composite material has a dielectric constant ≤ 2.45 @ 77 GHz, a dielectric loss < 0.0016, and an interfacial bonding strength ≥ 7.2 MPa.

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