Epoxy plastic packaging material with low linear expansion coefficient and preparation method thereof

Abstract

The application discloses an epoxy plastic sealing material with low linear expansion coefficient, which comprises the following components in percentage by mass: 5-10% of epoxy resin, 5-10% of curing agent, 70-90% of negative thermal expansion powder, 0.3-1% of silane coupling agent and 0.1-1% of curing accelerator; the negative thermal expansion powder is negative thermal expansion powder with adjustable thermal expansion coefficient. The epoxy plastic sealing material with ultra-low thermal expansion coefficient is prepared by adding the negative thermal expansion powder with adjustable thermal expansion coefficient as a functional filler in the epoxy plastic sealing material, and the high positive expansion of the epoxy resin matrix is actively offset by the negative expansion effect of the negative thermal expansion powder.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and in particular to epoxy molding compounds with low coefficient of linear expansion and their preparation methods. Background Technology

[0002] With the rapid development of electronic products towards miniaturization, high performance, and high reliability, semiconductor packaging technology faces unprecedented challenges and opportunities. Among various packaging forms, the Quad Flat No-Leader (QFN) package has become one of the mainstream packaging solutions for mid-to-high-end integrated circuits, such as microprocessors, power management chips, and RF chips, due to its advantages such as excellent electrical performance, good heat dissipation, small package size, and low cost. QFN packaging typically uses epoxy molding compound to encapsulate the chip, bonding wires, and lead frame into a single unit through a transfer molding process, achieving physical protection and environmental isolation for internal precision components.

[0003] However, the reliability of QFN packaging structures is highly dependent on the compatibility of the thermophysical properties of the constituent materials. As a major component of the package, the coefficient of thermal expansion (CTE) of the epoxy molding compound is a key parameter affecting reliability. Under varying temperature conditions, especially during chip soldering, reflow soldering processes in board-level assembly, and power cycling and thermal shocks during equipment service, significant differences in the CTE between the chip (typically silicon, CTE approximately 2.5 ppm / °C), leadframe (typically copper alloy, CTE approximately 17 ppm / °C), and traditional epoxy molding compounds (whose CTE below the glass transition temperature is typically 8-20 ppm / °C or even higher) can generate substantial thermal stress at the interface. This thermal stress can lead to a series of serious reliability problems, primarily including: Interface delamination: Delamination occurs at the bonding interface between the molding compound and the chip surface or the leadframe, severely affecting hermeticity and mechanical integrity. Chip cracking: Accumulated stress can cause cracks or even fractures in the brittle silicon chip, resulting in device malfunction. Solder joint fatigue: This issue is particularly prominent in ball-array packages, but for QFNs, thermal stress can also affect the reliability of the connection between the package and the PCB pads. Molding compound cracking: Under extreme stress, the molding compound itself may also crack. To reduce the coefficient of thermal expansion, the industry typically uses a method of adding a large amount of inorganic filler (such as fused silica) to the epoxy resin matrix. However, this method has significant limitations: a trade-off between processability and reliability: when the filler content is too high to achieve a sufficiently low CTE (e.g., requiring α1-CTE below 10 ppm / ℃), the melt viscosity of the epoxy molding compound increases sharply, leading to poor flowability and difficulty in filling complex, thin QFN cavities, easily resulting in defects such as unfilled areas and porosity. Simultaneously, high filler content negatively impacts the flexural strength and bond strength of the material.

[0004] Therefore, there is an urgent need in the field to develop a novel epoxy molding compound that can achieve a low coefficient of thermal expansion that is more compatible with the chip and leadframe while maintaining excellent molding processability and good mechanical properties, thereby fundamentally improving the long-term reliability of QFN packaged devices in harsh temperature environments. This invention is proposed based on this need.

[0005] Invention patent 202210498342.5 discloses a low-stress, low-water-absorption epoxy molding compound for semiconductor packaging and its preparation method, mainly comprising: 70-90 wt% filler, 5-15 wt% epoxy resin, 3-10 wt% phenolic resin curing agent, 0.2-0.8 wt% catalyst, and 1-5 wt% stress absorber. The preparation method can significantly reduce the modulus, thereby reducing thermal stress. However, data shows that reducing the modulus implies a reduction in strength. This is because the stress absorber has a rubber elastomer structure, with a glass transition temperature (Tg) much lower than that of the epoxy matrix. The patent discloses a coefficient of thermal expansion α1 between 11-14 ppm and α2 between 40-50 ppm.

[0006] CN202411734958.3 relates to a high-solids-content epoxy molding compound composition, a high-solids-content epoxy molding compound, its preparation method, and its application. The prepared epoxy molding compound has a high solids content and meets the requirements. Flame retardant rating, high thermal conductivity, low coefficient of thermal expansion, low water absorption, good insulation; contains 92% silica and o-cresyl epoxy resin, 6.6g polycyclic phenolic resin curing agent; coefficient of thermal expansion α1 = 5*10. -6 a2 = 30 * 10 -6 This patent requires adding up to 92% silica filler to the epoxy molding compound composition to reduce its coefficient of thermal expansion α1 to 5 ppm, while α2 remains as high as 30 ppm. Moreover, if the filler content is too high, the composition lacks fluidity and is difficult to fill the mold cavity during injection molding, resulting in a high defect rate.

[0007] Sumitomo CN202280011242.3 discloses a molding resin composition containing (A) epoxy resin, (B) a curing agent, and (C) an inorganic filler. The ratio of the linear expansion coefficient α1 at temperatures below the glass transition temperature to the linear expansion coefficient α2 at temperatures above the glass transition temperature, α1 / α2, is 0.40-1. The inventors, through the rational pairing of epoxy and curing agent, and the selection of various inorganic powders such as fused silica, crystalline silica, etc. (silica), alumina, talc, titanium oxide, silicon nitride, and aluminum nitride), have achieved a thermal expansion coefficient α1 between 4-6 ppm and α2 between 10-16 ppm. The combination of various inorganic powders and epoxy is crucial for reducing the thermal expansion coefficient and rationalizing the α1 / α2 ratio. Summary of the Invention

[0008] Based on the above, this invention proposes an epoxy molding compound with a low coefficient of linear expansion. The negative thermal expansion powder with an adjustable coefficient of thermal expansion is used as a functional filler. Through the negative expansion effect of the powder, the high positive expansion of the epoxy resin matrix is ​​actively offset, thereby preparing an EMC composite material with an ultra-low coefficient of thermal expansion.

[0009] To achieve the above objectives, the present invention provides the following technical solution: an epoxy molding compound with a low coefficient of linear expansion, comprising, by weight, the following components: 5-10% epoxy resin, 5-10% curing agent, 70-90% negative thermal expansion powder, 0.3-1% silane coupling agent, and 0.1-1% curing accelerator; the negative thermal expansion powder is a negative thermal expansion powder with an adjustable coefficient of thermal expansion.

[0010] Preferably, the particle size of the negative thermal expansion powder is 0.1μm - 100μm.

[0011] Preferably, the negative thermal expansion powder is one or more of tungstates, nepheline, zirconium molybdate, and zirconium phosphate.

[0012] Preferably, tungstates include, but are not limited to, doped zirconium tungstate or zirconium tungstate solid solutions or doped scandium tungstate or scandium tungstate solid solutions.

[0013] Preferably, nepheline includes β-nepheline solid solution and doped β-nepheline.

[0014] Preferably, the chemical formula of doped β-lithium nepheline is Li₂A₂. 1-x M x SiO 4-y F 2y A is Al 3+ M is B 3+ Ga 3+ Fe 3+ Cr 3+ ,Sc3+ One or more doping ions therein, x is the molar fraction of the doping ions at the M site, and 0 < x ≤ 0.25, F is a fluoride ion, substituting part of the oxygen ions, y is the fluorine substitution amount, 0 ≤ y ≤ 0.3.

[0015] For the doped β - eucryptite, the A site is Al 3+ , and the chemical general formula is LiAl 1-x M x SiO 4-y F 2y , and the synthesis method is as follows: The first step: Selection of raw materials and precursors Lithium source: Lithium carbonate Li2CO3, lithium nitrate LiNO3; Aluminum source: Alumina Al2O3 or aluminum hydroxide Al(OH)3; Al(OH)3 will decompose into highly active amorphous Al2O3 during heating, which helps to reduce the reaction temperature.

[0016] Silicon source: Silicon dioxide SiO2, usually high - purity and ultra - fine fumed silica or silica sol is selected to increase the specific surface area and improve the reaction activity; M is B 3+ , Ga 3+ , Fe 3+ , Cr 3+ , Sc 3+ One or more doping ions therein; B 3+ : Use boric acid H3BO3 or boron trioxide B2O ； They may volatilize at high temperatures, so an excessive amount needs to be added or a sealed crucible is used. Ga 3+ : Use gallium oxide Ga2O3; Fe 3+ : Use iron(III) oxide Fe2O3; Cr 3+ : Use chromium(III) oxide (Cr2O3); Sc 3+ : Use scandium oxide Sc2O3; Fluorine source (if y > 0): Use lithium fluoride LiF; it can provide both F - , and can also provide Li + , which can compensate for the possible lithium loss caused by volatilization.

[0017] The second step: Batching and mixing Chemical stoichiometric calculation: According to the general formula LiAl 1-x M x SiO 4-y F 2y , accurately calculate the mass of each raw material.

[0018] Grinding and mixing: Place the weighed powdered raw material into a ball mill jar (such as a polytetrafluoroethylene or zirconia jar), add an appropriate amount of anhydrous ethanol or acetone as a dispersion medium, use zirconia balls as grinding balls, and mix on a ball mill for 6-12 hours to ensure that the raw material achieves uniform mixing at the molecular level at the microscopic scale. After mixing, dry the slurry in an oven to obtain a uniformly mixed dry powder.

[0019] Tableting: The uniformly mixed dry powder is pressed into block or sheet form under appropriate pressure using a tablet press. This increases the contact area between raw materials, reduces volatilization, and prevents the powder from being carried away by airflow at high temperatures.

[0020] Step 3: Calcination (solid-phase reaction) The purpose of this step is to induce a solid-state reaction in the raw materials to generate the β-nepheline main crystal phase with the target crystal structure.

[0021] Temperature: The pressed blank is placed in an alumina crucible and calcined in a muffle furnace or box furnace at 1000℃ - 1200℃; the specific temperature depends on the type of doping element (x) and the fluorine content (y).

[0022] Atmosphere: Usually, it can be carried out in the air.

[0023] Time: The holding time is usually 2-10 hours. Too long a time may lead to excessive grain growth and lithium volatilization.

[0024] Heating / cooling rate: Programmable temperature control is used, with a heating rate of 2-5℃ / minute to prevent violent reaction leading to material spraying. After calcination, the furnace is cooled to room temperature.

[0025] Preferably, doped zirconium tungstate includes, but is not limited to, Ti. 4+ Doping, rare earth element doping, W-site doping of ZrW2O8; Ti 4+ Doping, chemical formula Zr 1-x Ti x W₂O₈, 0 ≤ x ≤ 0.4; rare earth element doped, chemical formula Zr 1-2x M x x W₂O₈, 0≤x≤1, where M is a +3 rare earth ion. Represents Zr vacancies; W-site doping, chemical formula ZrW 2-x M ox O8, 0≤x≤1; Zirconium tungstate solid solutions, including but not limited to Hf 4+ Doping, Hf 4+ Doping chemical formula Zr 1-x Hf x W₂O₈ solid solution, 0≤x≤1.

[0026] Preferred, doped scandium tungstate, chemical formula Sc 2-2x M 2x (WO4) 3-δ Where δ represents the trace anion vacancies generated to maintain charge balance, and M represents Al 3+ Fe 3+ or Cr 3+ 0.01 <x<0.25。

[0027] Preferred, doped scandium tungstate, chemical formula Sc2(W 1-y Mo y O4)3, where 0.05 ≤ y ≤ 0.40.

[0028] The preparation method of epoxy molding compound with low coefficient of linear expansion is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place epoxy resin, curing agent, surface-treated negative thermal expansion powder, curing accelerator and other additives in a mixing device according to the proportion, and mix thoroughly to obtain a mixture; the other additives are coupling agents; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 80-130℃ to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion; The epoxy resin is one or more of o-cresol type epoxy resin, bisphenol type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene phenol type epoxy resin, aralkyl phenol type epoxy resin, and naphthol type epoxy resin. The curing agent is a phenolic resin curing agent, which is one of linear phenolic resin, phenolic aryl phenolic resin, polyaromatic phenolic resin and polyfunctional phenolic resin; The coupling agent is one or more of trimethoxysilane, mercaptopropyltrimethoxysilane, phenylaminopropyltrimethoxysilane condensate, and propyltrimethoxysilane.

[0029] This invention creatively introduces inorganic powders with negative thermal expansion effects as functional fillers into epoxy resin matrices. By utilizing the physical property of fillers shrinking when heated, the inherent thermal expansion behavior of the epoxy resin matrix is ​​actively counteracted, thereby achieving precise control and significant reduction of its overall coefficient of thermal expansion at the composite material level. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to embodiments, but this is not intended to limit the invention in any way. Any modifications or improvements made based on the teachings of this invention fall within the protection scope of this invention. In solid-state chemistry and mineralogy, It is an internationally recognized symbol that indicates the location of missing atoms, such as the general chemical formula Zr in this article. 1-2x Sc 2x x W2O8, in which This represents a zirconium vacancy introduced to balance the charge.

[0031] Example 1: A low coefficient of linear expansion epoxy molding compound, comprising the following components by weight percentage: 6.6% polyaromatic epoxy resin (MAR), 4.5% phenolic biphenyl aralkyl resin as curing agent, and Sc as negative thermal expansion powder. 3+ doped zirconium tungstate powder (Zr 0.8 Sc 0.2 0.1 W₂O₈, a ≈ -6.8 × 10⁻⁶ -6 / K) 88%, coupling agent mercaptopropyltrimethoxysilane 0.4%, curing accelerator 2E4MZ 0.5%; negative thermal expansion powder Sc 3+ Zirconium tungstate, chemical formula Zr 1-2x Sc 2x x W2O8, in which This represents a zirconium vacancy, x = 0.10.

[0032] Sc 3+ Synthesis method of doped zirconium tungstate: a. Raw materials: according to Zr 0.8 Sc 0.2 0.1 The stoichiometric molar ratio of W2O8 is calculated by accurately weighing 0.8 mol of zirconium dioxide (ZrO2), 0.1 mol of scandium trioxide (Sc2O3), and 2.0 mol of tungsten trioxide (WO3). b. Mixing: Place the raw materials and anhydrous ethanol in a planetary ball mill jar, use zirconia balls as grinding balls, and ball mill for 8 hours to obtain a mixture; c. Pretreatment: The mixture obtained in step b is dried at 100°C and passed through a 200-mesh sieve to obtain powder; d. Sintering: Press the powder obtained in step c into an open alumina crucible and place it in a muffle furnace; heat it to 1150℃ at 5℃ / min in air atmosphere and hold it for 10 hours. e. Cooling: After the reaction is complete, the sample is taken out and rapidly cooled (quenched) in air to obtain a sintered block; f. Post-processing: The sintered mass obtained in step e is ground into Sc particles with a particle size D50 = 40 μm. 3+ Zirconium tungstate powder; Sc 3+ The coefficient of thermal expansion (CTE) of doped zirconium tungstate powder: Measured by thermomechanical analysis (TMA), its average volumetric thermal expansion coefficient α = -6.8 × 10⁻⁶ within the temperature range of 25-200°C. -6 / K, with a conductivity of 1.3 μS / cm.

[0033] The preparation method of epoxy molding compound with low coefficient of linear expansion is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place the multi-aromatic epoxy resin, curing agent phenol biphenyl aralkyl resin, surface-treated negative thermal expansion powder, curing accelerator 2E4MZ and coupling agent mercaptopropyltrimethoxy silane in a mixing device and mix thoroughly to obtain a mixture; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 100°C to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion.

[0034] The obtained epoxy molding compound with a low coefficient of linear expansion has a gelation time of 25 s, a flow length of 90 cm, and a coefficient of thermal expansion α1 of 1.0 × 10⁻⁶. -6 / K, coefficient of thermal expansion α2 = 3.2 × 10 -6 / K; Bending strength: 150MPa; Bending modulus: 16GPa; Defect rate % after TST500: 0; Defect rate % after TST1000: 0.

[0035] Example 2: A low linear expansion coefficient epoxy molding compound, comprising the following components by weight percentage: 6.6% polyaromatic epoxy resin (MAR), 4.5% curing agent phenol-biphenyl aralkyl resin, and Mo, a negative thermal expansion powder. 6+ The mixture contains 88% doped zirconium tungstate solid solution, 0.4% coupling agent mercaptopropyltrimethoxysilane, and 0.5% curing accelerator 2E4MZ; Mo 6+ General chemical formula for doped zirconium tungstate solid solutions: ZrW 2-x M ox O8, 0≤x≤1; Mo 6+ Synthesis method of doped zirconium tungstate solid solution: a. Raw materials: according to ZrW 2-x M ox With a stoichiometric molar ratio of O8 and x=0.4, accurately weigh 1 mol of zirconium dioxide (ZrO2), 1.6 mol of WO3, and 0.4 mol of MoO3. b. Mixing: Dry mixing for 6 hours using a high-energy planetary ball mill to achieve mechanical alloying pretreatment and obtain a mixture; c. Sintering: Press the mixture into tablets and seal them in vacuum-sealed quartz ampoules; d. Reaction: Place the ampoule in a furnace and heat to 1100°C, then keep warm for 24 hours; e. Cooling: After the reaction is complete, the ampoule is immersed in ice water for rapid water quenching to obtain the bulk material; f. Post-processing: Remove the block and grind it into powder with D50=50μm; The obtained Mo 6+ The coefficient of thermal expansion (CTE) of the zirconium tungstate solid solution: TMA tests show that, over a wide temperature range from -50°C to 300°C, its average bulk thermal expansion coefficient α = -8.2 × 10⁻⁶. -6 / K, with a conductivity of 1.1 μS / cm.

[0036] The preparation method of epoxy molding compound with low coefficient of linear expansion is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place the multi-aromatic epoxy resin, curing agent phenol biphenyl aralkyl resin, surface-treated negative thermal expansion powder, curing accelerator 2E4MZ and coupling agent mercaptopropyltrimethoxy silane in a mixing device and mix thoroughly to obtain a mixture; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 100°C to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion.

[0037] The obtained epoxy molding compound with a low coefficient of linear expansion has a gelation time of 24 s, a flow length of 104 cm, and a coefficient of thermal expansion α² = 0.8 × 10⁻⁶. -6 / K, coefficient of thermal expansion α2 = 2.4 × 10 -6 / K; Bending strength: 160MPa; Bending modulus: 15GPa; Defect rate % after TST500: 0; Defect rate % after TST1000: 0.

[0038] Example 3: A low linear expansion coefficient epoxy molding compound, comprising the following components by weight percentage: 6.6% polyaromatic epoxy resin (MAR), 4.5% curing agent phenol-biphenyl aralkyl resin, and negative thermal expansion powder Al. 3+ Scandium tungstate doping 88%, coupling agent mercaptopropyltrimethoxysilane 0.4%, curing accelerator 2E4MZ 0.5%; Al 3+ Scandium tungstate (scalar tungstate) 2-2x Al 2x (WO4) 3-δ Where δ represents the trace anion vacancies generated to maintain charge balance, 0.01 <x<0.25; Al 3+ Synthesis method of doped scandium tungstate: a. Raw materials: according to Sc 1.8 Al 0.2 (WO4) 2.9 According to the stoichiometric molar ratio, accurately weigh 0.9 mol scandium oxide Sc2O3, 0.1 mol aluminum oxide Al2O3 and 2.9 mol tungsten trioxide WO3; b. Mixing: Place the raw materials and anhydrous ethanol in a planetary ball mill jar, use zirconia balls as grinding balls, and ball mill for 10 hours to obtain a mixture; c. Pretreatment: The mixture is dried at 110℃ and passed through a 200-mesh sieve to obtain powder; d. Sintering: Press the powder into blocks, place them in an open alumina crucible, and put them into a muffle furnace; heat to 1000℃ at 3℃ / min in air atmosphere, and hold for 12 hours; e. Cooling: After the reaction is complete, the furnace is cooled to room temperature to obtain a sintered block; f. Post-processing: Grind the sintered block obtained in step e into powder with a particle size D50 = 55 μm; Al produced 3+ The average coefficient of thermal expansion of scandium tungstate-doped powder is α = -9.5 × 10⁻⁶. -6 / K, by changing the value of x in the general chemical formula from 0.05 to 0.20, α can be adjusted to -11.0 × 10 -6 / K to -8.5 × 10 -6 The conductivity is linearly adjustable within the range of / K, with a value of 1.5 μS / cm.

[0039] The preparation method of epoxy molding compound with low coefficient of linear expansion is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place the multi-aromatic epoxy resin, curing agent phenol biphenyl aralkyl resin, surface-treated negative thermal expansion powder, curing accelerator 2E4MZ and coupling agent mercaptopropyltrimethoxy silane in a mixing device and mix thoroughly to obtain a mixture; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 100°C to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion.

[0040] The obtained epoxy molding compound with a low coefficient of linear expansion has a gelation time of 26 s, a flow length of 94 cm, and a coefficient of thermal expansion α1 = 0.5 × 10⁻⁶. -6 / K, coefficient of thermal expansion α2 = 1.3 × 10 -6 / K; Bending strength: 152MPa; Bending modulus: 14GPa; Defect rate % after TST500: 0; Defect rate % after TST1000: 0.

[0041] Example 4: A low coefficient of linear expansion epoxy molding compound, comprising the following components by weight percentage: 6.6% polyaromatic epoxy resin (MAR), 4.5% curing agent phenol-biphenyl aralkyl resin, and Mo, a negative thermal expansion powder. 6+ Scandium tungstate doping 88%, coupling agent mercaptopropyltrimethoxysilane 0.4%, curing accelerator 2E4MZ 0.5%; Mo 6+ Scandium tungstate with the general chemical formula Sc2(W) 1-y Mo y O4)3, 0.05 ≤ y ≤ 0.40; Mo 6+ Synthesis method of doped scandium tungstate: a. Raw materials: according to Sc2(W 1-y Mo y Given a stoichiometric molar ratio of O4)3, y = 0.20, accurately weigh 1.0 mol scandium oxide Sc2O3, 0.6 mol MoO3, and 2.4 mol tungsten trioxide WO3; b. Mixing: Place the raw materials in a high-energy planetary ball mill and dry mix for 10 hours to ensure uniform mixing and obtain a mixture; c. Sintering: Press the mixture into tablets and place them in a sealed corundum crucible or a sealed quartz tube. Since MoO3 is volatile, it is necessary to isolate the atmosphere. d. For the reaction, place the crucible in a box furnace, heat to 1100℃, and hold for 15 hours; e. Cooling: After the reaction is complete, the furnace is cooled to room temperature to obtain a sintered block; f. Post-processing: Grind the sintered block into powder with a particle size D50 = 35μm.

[0042] The prepared Mo 6+ The coefficient of thermal expansion (CTE) of scandium tungstate-doped tungstate is measured by TMA, which shows that its average volumetric thermal expansion coefficient α = -10.2 × 10⁻⁶ over a wide temperature range of 25–800°C. -6 / K, with a conductivity of 1.8 μS / cm.

[0043] The preparation method of epoxy molding compound with low coefficient of linear expansion is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place the multi-aromatic epoxy resin, curing agent phenol biphenyl aralkyl resin, surface-treated negative thermal expansion powder, curing accelerator 2E4MZ and coupling agent mercaptopropyltrimethoxy silane in a mixing device and mix thoroughly to obtain a mixture; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 100°C to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion.

[0044] The obtained epoxy molding compound with a low coefficient of linear expansion has a gelation time of 25 s, a flow length of 96 cm, and a coefficient of thermal expansion α1 of 0.4 × 10⁻⁶. -6 / K, coefficient of thermal expansion α2 = 1.2 × 10 -6 / K; Bending strength: 170MPa; Bending modulus: 17GPa; Defect rate % after TST500: 0; Defect rate % after TST1000: 0.

[0045] Example 5: A low coefficient of linear expansion epoxy molding compound, comprising the following components by weight percentage: 6.6% polyaromatic epoxy resin (MAR), 4.5% curing agent phenol-biphenyl aralkyl resin, and negative thermal expansion powder B. 3+ The mixture contains 88% doped β-lithium nepheline, 0.4% coupling agent mercaptopropyltrimethoxysilane, and 0.5% curing accelerator 2E4MZ; B 3+ Doped β-lithium nepheline, chemical formula LiAl 1-x B x SiO4,0 <x ≤ 0.25; B 3+ Synthesis method of doped β-lithium nepheline: a. Raw materials: according to Li Al 1-x B xWeigh out lithium carbonate (Li2CO3) with chemical formula x = 0.05, and add an extra 3wt%; 0.475 mol aluminum oxide (Al2O3), 0.05 mol boric acid (H3BO3), and 1 mol silicon dioxide (SiO2); b. Mixing and pre-calcination: The raw materials are ball-milled with deionized water for 4 hours and then dried. They are then pre-calcined at 800°C for 2 hours to remove volatiles and obtain pre-calcined powder. c. Sintering: Press the pre-calcined powder into tablets, place them in a covered crucible, and sinter at 1250°C for 8 hours; d. Cooling: Cool to room temperature with the furnace; e. Post-processing: Grind and crush to a powder with D50 = 48μm.

[0046] The thermal expansion coefficient (CTE) of the B³⁺-doped β-lithium nepheline was determined by TMA testing. The results showed that, over a wide temperature range of 25–800°C, the C-axis thermal expansion coefficient α = -16.2 × 10⁻⁶. -6 / K, with a conductivity of 1.2 μS / cm.

[0047] The preparation method of epoxy molding compound with low coefficient of linear expansion is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place the multi-aromatic epoxy resin, curing agent phenol biphenyl aralkyl resin, surface-treated negative thermal expansion powder, curing accelerator 2E4MZ and coupling agent mercaptopropyltrimethoxy silane in a mixing device and mix thoroughly to obtain a mixture; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 90°C to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion.

[0048] The obtained epoxy molding compound with a low coefficient of linear expansion has a gelation time of 23 s, a flow length of 100 cm, and a coefficient of thermal expansion α1 of 0.3 × 10⁻⁶. -6 / K, coefficient of thermal expansion α2 = 0.7 × 10 -6 / K; Bending strength: 175MPa; Bending modulus: 19GPa; Defect rate % after TST500: 0; Defect rate % after TST1000: 0.

[0049] Example 6: A low coefficient of linear expansion epoxy molding compound, comprising the following components by weight percentage: 6.6% polyaromatic epoxy resin (MAR), 4.5% curing agent phenol-biphenyl aralkyl resin, and F-type negative thermal expansion powder. -The mixture contains 88% doped β-lithium nepheline, 0.4% coupling agent mercaptopropyltrimethoxysilane, and 0.5% curing accelerator 2E4MZ; F - Doped β-lithium nepheline, chemical formula LiAlSiO 4-y F 2y , 0 ≤ y ≤ 0.3; F - Synthesis method of doped β-lithium nepheline: a. Raw materials: LiAlSiO 4-y F 2y The chemical formula of lithium nitrate (LiNO3) and aluminum isopropoxide (C9H3O) is given, with y = 0.1. 21 AlO3, tetraethyl orthosilicate (TEOS), and ammonium fluoride (NH4F) are used as precursors, and their molar ratios are calculated according to their chemical formulas. b. Sol-gel: TEOS is dissolved in ethanol and hydrolyzed, and then an ethanol solution of aluminum isopropoxide, an aqueous solution of LiNO3 and an aqueous solution of NH4F are added in sequence and stirred to form a homogeneous sol. c. Gelation and drying: The sol was aged at 60°C for 24 hours to form a gel, and then dried at 100°C to obtain the precursor; d. Calcination: The precursor powder was calcined at 900°C for 3 hours; e. Post-processing: Grind to a powder with D50 = 25μm.

[0050] The obtained F - The thermal expansion coefficient (CTE) of doped β-lithium nepheline is shown by TMA testing to be -16.8 × 10⁻⁶ along the c-axis, with a coefficient of thermal expansion α of -16.8 × 10⁻⁶ over a wide temperature range of 25–500°C. -6 / K, with a conductivity of 1.7 μS / cm.

[0051] The preparation method of epoxy molding compound with low coefficient of linear expansion is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place the multi-aromatic epoxy resin, curing agent phenol biphenyl aralkyl resin, surface-treated negative thermal expansion powder, curing accelerator 2E4MZ and coupling agent mercaptopropyltrimethoxy silane in a mixing device and mix thoroughly to obtain a mixture; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 90°C to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion.

[0052] The obtained epoxy molding compound with a low coefficient of linear expansion has a gelation time of 20 s, a flow length of 102 cm, and a coefficient of thermal expansion α1 of 0.3 × 10⁻⁶. -6 / K, coefficient of thermal expansion α2 = 0.7 × 10 -6 / K; Bending strength: 163MPa; Bending modulus: 14GPa; Defect rate % after TST500: 0; Defect rate % after TST1000: 0.

[0053] Example 7: A low coefficient of linear expansion epoxy molding compound, comprising the following components by weight percentage: 6.6% polyaromatic epoxy resin (MAR), 4.5% curing agent phenol-biphenyl aralkyl resin, and Ga negative thermal expansion powder. 3+ 88% doped β-lithium nepheline, 0.6% coupling agent mercaptopropyltrimethoxysilane, and 0.3% curing accelerator 2E4MZ; Ga 3+ Doped β-lithium nepheline, chemical formula LiAl 1-x Ga x SiO4,0 <x ≤ 0.25; Ga 3+ Synthesis method of doped β-lithium nepheline: a. Raw materials: according to Li Al 1-x Ga x SiO4, x = 0.1, according to the chemical formula molar ratio: Li2CO3:Al2O3:Ga2O3:SiO2 = 0.5:0.45:0.05; b. Mixing: Place the weighed raw materials in a nylon ball mill jar, add anhydrous ethanol as the dispersion mass, use zirconia balls as milling balls, and ball mill and mix at 300 rpm for 6 hours on a planetary ball mill to achieve a homogeneous mixture at the molecular level. c. Pre-calcination: The mixture is placed in an alumina crucible and pre-calcined at 800°C in air for 2 hours to completely decompose lithium carbonate and preliminarily activate the reaction to obtain powder; d. Sintering: The pre-calcined powder is ground again and pressed into blocks; the blocks are placed in a covered corundum crucible, which is covered to effectively suppress the volatilization of lithium; the crucible is placed in a box furnace and heated to 1250°C at a heating rate of 5°C / min in air atmosphere, and held at this temperature for 10 hours to complete the solid-state reaction and crystal growth. e. Post-processing: ball milling, obtaining particle size through air classification, and grinding to powder with D50 ≈20μm.

[0054] Ga produced 3+ The thermal expansion coefficient (CTE) of doped β-lithium nepheline is shown by TMA testing to be -15.2 × 10⁻⁶ C-axis direction, with a coefficient of thermal expansion α of -15.2 × 10⁻⁶ over a wide temperature range of 25–500 °C. -6 / K, with a conductivity of 1.6 μS / cm.

[0055] The preparation method of epoxy molding compound with low coefficient of linear expansion is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place the multi-aromatic epoxy resin, curing agent phenol biphenyl aralkyl resin, surface-treated negative thermal expansion powder, curing accelerator 2E4MZ and coupling agent mercaptopropyltrimethoxy silane in a mixing device and mix thoroughly to obtain a mixture; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 95°C to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion.

[0056] The obtained epoxy molding compound with a low coefficient of linear expansion has a gelation time of 21 s, a flow length of 100 cm, and a coefficient of thermal expansion α1 of 0.3 × 10⁻⁶. -6 / K, coefficient of thermal expansion α2 = 0.9 × 10 -6 / K; Bending strength: 172MPa; Bending modulus: 15GPa; Defect rate % after TST500: 0; Defect rate % after TST1000: 0.

[0057] Comparative Example: A low linear expansion coefficient epoxy molding compound, by mass percentage, comprising the following components: 6.6% polyaromatic epoxy resin (MAR), 4.5% curing agent phenol-biphenyl aralkyl resin, 88% spherical silica, 0.4% coupling agent mercaptopropyltrimethoxysilane, and 0.5% curing accelerator 2E4MZ; Preparation method of epoxy molding compound with low coefficient of linear expansion: a. Powder surface treatment: spherical silica is surface modified with a silane coupling agent to obtain surface-treated powder; b. Mixing: Place the multi-aromatic epoxy resin, curing agent phenol biphenyl aralkyl resin, surface-treated powder, curing accelerator 2E4MZ and coupling agent mercaptopropyltrimethoxy silane in a mixing device and mix thoroughly to obtain a mixture; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 90°C to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion; The prepared epoxy molding compound with a low coefficient of linear expansion had a gelation time of 22 s, a flow length of 104 cm, and a coefficient of thermal expansion α1 of 11 × 10⁻⁶. -6 / K, coefficient of thermal expansion α2 = 36×10 -6 / K; Bending strength: 161MPa; Bending modulus: 15GPa; Defect rate % after TST500: 5; Defect rate % after TST1000: 16.

[0058] Table 1: Parameter and performance table of epoxy molding compounds with low coefficient of linear expansion obtained in Examples 1-7: The test method for the performance of epoxy molding compound with low coefficient of linear expansion in this invention is as follows: Gelation time determination method: Place 1.0g of epoxy molding compound powder on a heating plate at 175±1℃. Start timing when the sample melts, and press continuously with a flat spatula. Stop timing when it becomes gelled.

[0059] Spiral flow length: At 175℃ and with the transmission pressure set to 6.9MPa, epoxy molding compound powder is injected into a spiral flow length test mold preheated to the same temperature through a transfer molding press, and the length of the longest continuous point is read.

[0060] Method for determining the coefficient of linear expansion: Using a transfer molding machine, the molding resin composition was injected and molded under the conditions of mold temperature 175℃, injection pressure 9.8MPa, and curing time 120 seconds to obtain a test piece with a length of 15mm × width of 4mm × thickness of 4mm. After curing the test piece at 175℃ for 4 hours, the coefficient of linear expansion was measured using a thermomechanical analysis device in compression mode under the conditions of a measurement temperature range of 0℃~320℃ and a heating rate of 5℃ / min. Based on the measurement results, the average coefficient of linear expansion from 40℃ to 80℃ was calculated as CTE1, and the average coefficient of linear expansion from 190℃ to 230℃ was calculated as CTE2.

[0061] Bending strength test method: GB / T9341 is adopted, the load application speed is 2mm / min, and the load value is read when the cured epoxy molding compound sample breaks.

[0062] Flexural modulus determination method: The TA DMA850 dynamic thermomechanical analyzer was used for testing. The test mode was three-point bending mode with fixed amplitude oscillation, preload force of 0.5N, heating rate of 3℃ / min, 25-280℃, and sample size of 3*15*50mm. Modulus data were read at 25℃ and 260℃.

[0063] Measurement of ion content of powder: Weigh 5g of powder into 95ml of measured deionized water using a balance, stir with a magnetic stir bar for 30 minutes, and then measure the conductivity. Subtract the conductivity value of the deionized water to get the conductivity value of the powder sample, which is generally ≤5μS / cm.

[0064] QFN chips were packaged using a high-temperature molding and curing method (curing at 175°C for 90 minutes, then at 175°C for 6-8 hours). The QFN chips were then subjected to a thermal shock test (TST) by maintaining them at -55°C for 10 minutes, followed by a 10-minute maintenance at 125°C. Ultrasonic images of the chips were obtained using an ultrasonic scanner (Nordson, D9650) after 500 (TST500) and 1000 (TST1000) cycles of this procedure. In areas of peeling (void, missing adhesive), the signal is very strong due to near total reflection of ultrasound in air / vacuum, typically appearing as a bright color. A threshold was set at a point that clearly distinguishes between "good adhesion" and "defects (peeling)". All pixels with signal strength exceeding this threshold were identified by the software as "defects" (i.e., peeling areas). Total peeling area...

Claims

1. An epoxy molding compound with a low coefficient of linear expansion, characterized in that, The product comprises, by weight percentage, the following components: 5-10% epoxy resin, 5-10% curing agent, 70-90% negative thermal expansion powder, 0.3-1% silane coupling agent, and 0.1-1% curing accelerator; wherein the negative thermal expansion powder is a negative thermal expansion powder with an adjustable coefficient of thermal expansion.

2. The epoxy molding compound with a low coefficient of linear expansion according to claim 1, characterized in that... The particle size of the negative thermal expansion powder is 0.1μm - 100μm.

3. The epoxy molding compound with a low coefficient of linear expansion according to claim 1, characterized in that... The negative thermal expansion powder is one or more of tungstates, lithium nepheline, zirconium molybdate, and zirconium phosphate.

4. The epoxy molding compound with a low coefficient of linear expansion according to claim 3, characterized in that... The tungstates mentioned include, but are not limited to, doped zirconium tungstate or zirconium tungstate solid solutions or doped scandium tungstate or scandium tungstate solid solutions.

5. The epoxy molding compound with a low coefficient of linear expansion according to claim 3, characterized in that... The aforementioned nepheline-type minerals include β-nepheline solid solutions and doped β-nepheline.

6. The epoxy molding compound with a low coefficient of linear expansion according to claim 5, characterized in that... The chemical formula of the doped β-lithium nepheline is LiA. 1-x M x SiO 4-y F 2y A is Al 3+ M is B 3+ Ga 3+ Fe 3+ Cr 3+ ,Sc 3+ One or more doped ions are included, where x is the mole fraction of the M-site doped ion and 0 < x ≤ 0.25, F is a fluoride ion that partially replaces oxygen ions, and y is the amount of fluoride substitution and 0 ≤ y ≤ 0.

3.

7. The epoxy molding compound with a low coefficient of linear expansion according to claim 4, characterized in that... The doped zirconium tungstate includes, but is not limited to, Ti. 4+ Doping, rare earth element doping, W-site doping of ZrW2O8; Ti 4+ Doping, general chemical formula Zr 1- x Ti x W₂O₈, 0 ≤ x ≤ 0.4; rare earth element doped, chemical formula Zr 1-2x M x x W₂O₈, 0≤x≤1, where the M-site is a +3 valent rare earth ion. Represents Zr vacancies; W-site doping in ZrW₂O₈, with the general chemical formula ZrW 2-x M ox O8, 0≤x≤1; The zirconium tungstate solid solution includes, but is not limited to, Hf 4+ Doping; Hf 4+ Doping chemical formula Zr 1-x Hf x W₂O₈ solid solution, 0≤x≤1.

8. The epoxy molding compound with a low coefficient of linear expansion according to claim 4, characterized in that... The doped scandium tungstate, with the general chemical formula Sc 2-2x M 2x (WO4) 3-δ Where δ represents the trace anion vacancies generated to maintain charge balance, and M represents Al 3+ Fe 3+ or Cr 3+ 0.01 <x<0.25。 9. The epoxy molding compound with a low coefficient of linear expansion according to claim 4, characterized in that... The doped scandium tungstate described herein has the general chemical formula Sc2(W 1-y Mo y O4)3, where 0.05 ≤ y ≤ 0.

40.

10. A method for preparing an epoxy molding compound with a low coefficient of linear expansion as described in any one of claims 1-9, characterized in that... The preparation method is as follows: a. Powder surface treatment: The negative thermal expansion powder is surface modified with a silane coupling agent to obtain the negative thermal expansion powder after surface treatment; b. Mixing: Place epoxy resin, curing agent, surface-treated negative thermal expansion powder, curing accelerator and other additives in a mixing device according to the proportion, and mix thoroughly to obtain a mixture; the other additives are coupling agents; c. Mixing: Place the mixture in a two-roll mill or extruder and mix at 80-130℃ to fully plasticize it and ensure that the filler is evenly dispersed; d. Cooling and crushing: Cool and crush the material from step C to obtain an epoxy molding compound with a low coefficient of linear expansion; The epoxy resin is one or more of o-cresol type epoxy resin, bisphenol type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene phenol type epoxy resin, aralkyl phenol type epoxy resin, and naphthol type epoxy resin. The curing agent is a phenolic resin curing agent, which is one of linear phenolic resin, phenolic aryl phenolic resin, polyaromatic phenolic resin and polyfunctional phenolic resin; The coupling agent is one or more of trimethoxysilane, mercaptopropyltrimethoxysilane, phenylaminopropyltrimethoxysilane condensate, and hydroglycerol ether propyltrimethoxysilane.

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