High-thermal-conductivity low-shrinkage chip underfill composition and preparation method thereof

Abstract

The invention relates to the technical field of electronic packaging materials, in particular to a high-thermal-conductivity low-shrinkage chip underfill composition and a preparation method thereof.The composition comprises bisphenol F type epoxy resin (20%-30%), three-peak spherical aluminum oxide (55%-65%), surface modified silicon nitride (3%-5%), a latent anhydride curing agent (5%-8%) and a functional additive (2%-4%), according to the high-thermal-conductivity low-shrinkage chip underfill composition and the preparation method thereof, vertical directional arrangement of silicon nitride is realized through a magnetic field auxiliary process, so that the heat conductivity coefficient in the vertical direction is greater than or equal to 3.0 W / m.K, the curing shrinkage rate is less than or equal to 1.0%, and the total weight percentage of the components is strictly 100%.

Description

Technical Field

[0001] The invention relates to the technical field of electronic packaging materials, in particular to a high-thermal-conductivity, low-shrinkage chip underfill composition and a preparation method thereof. Background Art

[0002] The chip underfill composition is an important material used in chip packaging. Its main function is to alleviate the stress concentration problem caused by the mismatch of thermal expansion coefficients between different materials in chip packaging, thereby improving the reliability of device packaging. The chip underfill composition usually contains a variety of ingredients to ensure that it has good fluidity, high reliability, low thermal expansion coefficient and other properties. These ingredients may include resins, fillers, curing agents, accelerators, coupling agents and other additives.

[0003] Traditional underfill has the following defects: 1. Insufficient thermal conductivity: thermal conductivity of silicon powder <1 W / m·K (cited patent: US 8,883,234); 2. High shrinkage: curing shrinkage >1.5% (cited patent: JP 2020-156789A); 3. Filler sedimentation: The viscosity of highly filled systems is unstable (cited patent: CN 104177945A).

[0004] Existing improvement schemes such as patent US 20180155434B1 propose multi-peak silicon powder filling, but the thermal conductivity is still lower than 2.0 W / m·K. Summary of the invention

[0005] The object of the present invention is to provide a high thermal conductivity and low shrinkage chip underfill composition and a preparation method thereof, so as to solve the problems of insufficient thermal conductivity, high shrinkage and filler sedimentation proposed in the above background technology. To achieve the above object, the present invention provides the following technical solution: a high thermal conductivity and low shrinkage chip underfill composition and a preparation method thereof, comprising, by weight percentage: Bisphenol F type epoxy resin (20%-30%): epoxy equivalent 160-180 g / eq, viscosity <500 mPa·s; Trimodal spherical alumina (Al2O3) (55%-65%): particle size distribution is 10μm (accounting for 50%-70% of itself), 5μm (20%-30%), 0.5μm (5%-10%); Surface modified silicon nitride (Si3N4) (3% to 5%): treated with aminosilane (KH550), particle size 1-3μm; Latent curing agent (5% to 8%): mass ratio of tetrahydrophthalic anhydride (THPA) to microencapsulation accelerator (2E4MZ-CN) (5-7): 1; Functional additives (2% to 4%): modified montmorillonite (anti-settling), polyethersulfone (toughening), fluorinated silane (moisture resistance).

[0006] The particle size mass ratio of the trimodal spherical alumina is 10 μm: 5 μm: 0.5 μm = (5-7): (2-3): 1.

[0007] The amino group density of the surface-modified silicon nitride is 0.5-1.0 mmol / g, and the magnetic field orientation intensity is 0.8-1.2T.

[0008] The latent curing agent is tetrahydrophthalic anhydride and microencapsulated 2-ethyl-4-methylimidazole derivative, with a mass ratio of (5-7):1.

[0009] A method for preparing the underfill comprises the following steps: a) performing aminosilane surface treatment on silicon nitride; b) mixing bisphenol F epoxy resin with a functional additive; c) adding trimodal alumina, modified silicon nitride and montmorillonite, and applying a 0.8-1.2T vertical magnetic field for orientation for 10 minutes after dispersion; d) Add latent curing agent, vacuum degassing and then encapsulate.

[0010] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, the magnetic field-assisted process realizes the vertical oriented arrangement of silicon nitride, so that the thermal conductivity in the vertical direction is ≥3.0 W / m·K, the curing shrinkage is ≤1.0% (density method), the viscosity is <700 mPa·s (25°C), there is no sedimentation (viscosity change after standing for 7 days is <5%), the water absorption rate is <0.1% (85°C / 85%RH, 24h), and the total weight percentage of the components is strictly 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a SEM image of the filler distribution of trimodal alumina and oriented silicon nitride of the present invention (the particle size distribution ratio is: 10 μm: 5 μm: 0.5 μm); Figure 2 Comparison of thermal conductivity in vertical and horizontal directions of the present invention (Example 1 vs. traditional formula). DETAILED DESCRIPTION

[0012] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technical personnel in this field without creative work are within the scope of protection of the present invention.

[0013] Example 1 Preparation method: 1. Filler pretreatment: - Immerse Si3N4 in 5% KH550 ethanol solution for ultrasonic treatment for 1 hour and dry at 80℃; 2. Resin mixing: - Mix bisphenol F epoxy resin, PES and fluorinated silane and stir at 40°C for 30 minutes; 3. Filler dispersion and magnetic field orientation: - Add Al2O3, Si3N4, montmorillonite, and degassing by planetary stirring (vacuum degree ≤ 0.1 MPa, 30 minutes); - Apply a 1T vertical magnetic field for 10 minutes to align the Si3N4 sheets vertically; 4. Add curing agent: - Add THPA and microencapsulated 2E4MZ-CN, stir for 20 minutes, fill and store in a dark place.

[0014] Performance test results: Thermal conductivity (vertical): 3.0 W / m·K; Viscosity: 620 mPa·s (25°C); Shrinkage rate: 0.9%; Water absorption rate: 0.1%; Sedimentation stability: Viscosity changes by 3.5% after standing for 7 days.

[0015] The above shows and describes the basic principles, main features and advantages of the present invention. Technical personnel in this industry should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high thermal conductivity and low shrinkage chip underfill composition, characterized in that: Included by weight percentage: 20% to 30% bisphenol F epoxy resin; 55% to 65% trimodal spherical alumina with particle size distribution of 10μm, 5μm, and 0.5μm; 3% to 5% surface-modified silicon nitride treated with aminosilane; 5% to 8% latent anhydride curing agent; 2% to 4% of functional additives, including modified montmorillonite, polyethersulfone and fluorinated silane.

2. The composition according to claim 1, characterized in that The particle size mass ratio of the trimodal spherical alumina is 10 μm: 5 μm: 0.5 μm = (5-7): (2-3):

1.

3. The composition according to claim 1, characterized in that The amino group density of the surface-modified silicon nitride is 0.5-1.0 mmol / g, and the magnetic field orientation intensity is 0.8-1.2T.

4. The composition according to claim 1, characterized in that The latent curing agent is tetrahydrophthalic anhydride and microencapsulated 2-ethyl-4-methylimidazole derivative, with a mass ratio of (5-7):

1.

5. A method for preparing the underfill according to claims 1-4, comprising the following steps: a) performing aminosilane surface treatment on silicon nitride; b) mixing bisphenol F epoxy resin with a functional additive; c) adding trimodal alumina, modified silicon nitride and montmorillonite, and applying a 0.8-1.2T vertical magnetic field for orientation for 10 minutes after dispersion; d) Add latent curing agent, vacuum degassing and then encapsulate.

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