Low-coefficient-of-expansion chip-level single-component epoxy underfill adhesive and application thereof

Abstract

The present application relates to an adhesive and its application, specifically relates to a kind of low expansion coefficient's chip level single-component epoxy underfill adhesive and its application;The raw material of the underfill adhesive includes by mass fraction: matrix epoxy resin 80~100 parts, anthracene modified chitosan toughening agent 5~15 parts, low viscosity epoxy resin 2~10 parts;It also includes chitosan modified filler and curing agent;The reaction activity of chitosan is changed in anthracene modified chitosan toughening agent by modifying the primary amine group of chitosan, can form covalent crosslinking network with the matrix epoxy resin containing a certain amount of anthracene resin, can significantly reduce the thermal expansion coefficient of system, while improving the thermal stability, mechanical properties and interface compatibility of material, can effectively alleviate the device failure problem caused by thermal stress.

Description

Technical Field

[0001] This invention relates to an adhesive and its application, specifically to a one-component epoxy underfill adhesive and its application. Background Technology

[0002] In semiconductor chip packaging processes, underfill adhesive is a critical material used to fill the gap between the chip and the substrate, alleviating thermal stress caused by the difference in coefficients of thermal expansion (CTE) between the chip and the substrate. This prevents chip solder joint cracking and device failure, ensuring the long-term reliability of semiconductor devices. Current chip-level packaging has extremely stringent CTE requirements for underfill adhesive. The CTE difference between the chip and the substrate (such as ceramic or PCB substrates) is relatively small. If the CTE of the underfill adhesive is too high, it is easy to generate large internal stress during temperature cycling, leading to solder joint detachment.

[0003] Traditional epoxy underfillers often use bisphenol A / B type epoxy resin as the matrix, combined with fillers such as silica powder and aluminum hydroxide to reduce CTE, but they have the following drawbacks:

[0004] (1) The resin matrix itself has a high CTE (especially below the glass transition temperature). Simply relying on fillers cannot achieve a significant reduction in CTE. Moreover, excessive fillers can easily lead to a sudden increase in system viscosity and a decrease in fluidity, affecting the filling effect.

[0005] (2) The filler has poor interfacial compatibility with the epoxy resin matrix, which makes it easy to agglomerate and settle, resulting in an increase in internal defects of the material and a decrease in mechanical properties (such as tensile strength and impact toughness) and thermal stability.

[0006] (3) In order to improve rigidity and thermal stability, some solutions introduce polycyclic aromatic resins, but this can easily lead to increased material brittleness. Excessive introduction can cause excessive cross-linking and generate internal stress, which can slow down or even rebound the CTE reduction.

[0007] (4) Traditional curing agents (such as polyetheramine series) have limited compatibility with resins and fillers, making it difficult to synergistically reduce CTE. Furthermore, the Tg (glass transition temperature) of the cured material is low, and the molecular chain movement is intense at high temperatures, further exacerbating the problem of high CTE. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a chip-level single-component epoxy underfill adhesive with low CTE and high Tg and its application.

[0009] The technical solution adopted by the present invention to solve its technical problem is as follows: a chip-level single-component epoxy underfill adhesive with low expansion coefficient, the raw materials include, by mass parts: 80-100 parts of matrix epoxy resin, 5-15 parts of anthracene-modified chitosan toughening agent, 2-10 parts of low viscosity epoxy resin, and also include chitosan modified filler and curing agent.

[0010] The matrix epoxy resin includes bisphenol-type epoxy resin and anthracene-based resin; the anthracene-based resin has an anthracene ring structure and accounts for 5wt%~15wt% of the matrix epoxy resin.

[0011] The chemical structure of the anthracene-modified chitosan toughening agent is as follows: based on chitosan A1, the hydrogen in the primary amine group is replaced by group A2, so that the primary amine group forms a secondary amine group; the primary amine group to be replaced is all or part of the primary amine groups in chitosan A1; the structure of chitosan A1 is as follows:

[0012] ;

[0013] Where n = 1~15;

[0014] The group A2 is

[0015] ;

[0016] Wherein R represents one of H, C1~C12 alkyl, C1~C12 alkoxy, substituted aryl, unsubstituted aryl, substituted aryloxy, and unsubstituted aryloxy.

[0017] R' represents one of H, C1~C12 alkyl, substituted aryl, or unsubstituted aryl;

[0018] This indicates that the location is a half bond.

[0019] Preferably, the bisphenol type epoxy resin includes one or more of bisphenol S type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, and linear phenolic epoxy resin.

[0020] Preferably, the low-viscosity epoxy resin includes one or more of the following: monoepoxy propenyl glycidyl ether, phenyl glycidyl ether, diepoxy ethylene glycol diglycidyl ether, resorcinol diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0021] Preferably, the curing agent comprises a compound having structure B, wherein structure B is:

[0022] ;

[0023] Wherein R1 represents one of H, C1~C12 alkyl, C1~C12 alkoxy, substituted aryl, unsubstituted aryl, substituted aryloxy, and unsubstituted aryloxy.

[0024] Preferably, the amount of curing agent is: the ratio of the mass of curing agent to the molar amount of epoxy groups in the matrix epoxy resin is 38g~57g:1mol.

[0025] Preferably, the chitosan-modified filler is obtained by mixing and pulverizing an inorganic filler with chitosan.

[0026] Preferably, the amount of chitosan-modified filler is 30-70 parts by weight (relative to 80-100 parts by weight of the matrix epoxy resin).

[0027] Preferably, the mass ratio of inorganic filler to chitosan in the chitosan-modified filler is 7~15:1.

[0028] Preferably, the average molecular weight of chitosan in the chitosan-modified filler is 50kDa to 150kDa.

[0029] Preferably, the raw materials of the low expansion coefficient chip-level single-component epoxy underfill adhesive also include 0-5 parts of dispersant, 0-2 parts of defoamer, and 0-2 parts of colorant.

[0030] Preferably, the low expansion coefficient chip-level single-component epoxy underfill adhesive is made by uniformly mixing the raw materials.

[0031] Based on the same inventive concept, this invention also provides the application of the low expansion coefficient chip-level single-component epoxy underfill adhesive in semiconductor chip packaging.

[0032] Preferably, it is used for chip-scale packaging (CSP) and / or flip-chip.

[0033] The present invention has the following beneficial effects:

[0034] Anthracene-modified chitosan toughening agent modifies the primary amine group of chitosan A1 with group A2 to form a secondary amine group, thereby changing the reactivity of chitosan A1. It can form a covalent cross-linked network with a matrix epoxy resin containing a certain amount of anthracene-based resin. The above components work synergistically to significantly reduce the coefficient of thermal expansion (CTE) of the system, especially below Tg, the CTE is reduced by more than 10 ppm / ℃ compared with the traditional system. At the same time, it improves the thermal stability, mechanical properties and interfacial compatibility of the material. The product has a high Tg and is suitable for chip-level packaging, which can effectively alleviate the device failure problem caused by thermal stress.

[0035] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0036] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 This is the anthracene-modified chitosan toughening agent TM1 prepared in the embodiments of the present invention. 1 H-NMR spectrum;

[0038] Figure 2 This is the anthracene-modified chitosan toughening agent TM1 prepared in the embodiments of the present invention. 13 C-NMR spectrum. Detailed Implementation

[0039] To make the objectives, solutions, and beneficial technologies of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be noted that the embodiments described in this specification are merely illustrative of the invention and are not intended to limit the invention.

[0040] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0041] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, "multiple" in "one or more" means two or more, and "more than" in "one or more" means two or more.

[0042] An embodiment of the present invention provides a chip-level single-component epoxy underfill adhesive with a low coefficient of thermal expansion. By weight, the raw materials include: 80-100 parts of matrix epoxy resin, 5-15 parts of anthracene-modified chitosan toughening agent, 2-10 parts of low viscosity epoxy resin, and also include chitosan modified filler and curing agent.

[0043] The matrix epoxy resin includes bisphenol-type epoxy resin and anthracene-based resin; the anthracene-based resin has an anthracene ring structure and accounts for 5wt%~15wt% of the matrix epoxy resin.

[0044] The chemical structure of the anthracene-modified chitosan toughening agent is as follows: based on chitosan A1, the hydrogen in the primary amine group is replaced by group A2, so that the primary amine group forms a secondary amine group; the primary amine group to be replaced is all or part of the primary amine groups in chitosan A1; the structure of chitosan A1 is as follows:

[0045] ;

[0046] Where n = 1~15;

[0047] The group A2 is

[0048] ;

[0049] Wherein R represents one of H, C1~C12 alkyl, C1~C12 alkoxy, substituted aryl, unsubstituted aryl, substituted aryloxy, and unsubstituted aryloxy.

[0050] R' represents one of H, C1~C12 alkyl, substituted aryl, or unsubstituted aryl;

[0051] This indicates that the location is a half bond.

[0052] The anthracene-modified chitosan toughening agent in this solution modifies the primary amine group of chitosan A1 with group A2 to form a secondary amine group, thereby changing the reactivity of chitosan A1. It can form a covalent cross-linked network with the matrix epoxy resin containing a certain amount of anthracene-based resin. The synergistic effect of the above components can achieve the following results:

[0053] (1) Significantly reduced CTE: The polycyclic rigid structure of anthracene resin reduces free volume through steric hindrance, and the modified chitosan and epoxy resin form a dense cross-linked network to inhibit molecular chain movement, resulting in a reduction of more than 10 ppm / ℃ in CTE below Tg compared to the traditional system.

[0054] (2) Improved thermal stability: The polycyclic aromatic structure of anthracene resins gives them excellent resistance to high-temperature decomposition. The cross-linking effect of modified chitosan and epoxy resin improves the regularity of molecular chains, which significantly increases the thermal decomposition temperature and Tg of the material.

[0055] (3) Balanced mechanical properties: The flexible segments of modified chitosan alleviate the brittleness of epoxy resin, and the rigid structure of anthracene resin provides a high-strength skeleton. Combined with the reinforcing effect of fillers, the tensile strength and impact toughness of the material are better than those of single-component epoxy systems.

[0056] (4) Excellent dispersibility and compatibility: Chitosan-modified filler can improve the compatibility between filler and system, reduce filler agglomeration, and improve interfacial compatibility between modified chitosan and epoxy resin through hydrogen bonds or covalent bonds, reduce internal defects, and ensure long-term reliability of materials.

[0057] The polycyclic structure of the anthracene resin in this scheme can be uniformly dispersed in the bisphenol epoxy resin, reducing the free volume of the system through the steric hindrance effect, thereby reducing the CTE. However, if the amount added is too high, it will also cause the viscosity of the system to increase sharply, making dispersion difficult, or causing internal stress due to excessive crosslinking, resulting in a slowdown or even a rebound in the reduction of CTE.

[0058] In embodiments of the present invention, the bisphenol type epoxy resin includes one or more of bisphenol S type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, and linear phenolic epoxy resin.

[0059] In embodiments of the present invention, the low-viscosity epoxy resin includes one or more of the following: monoepoxy propenyl glycidyl ether, phenyl glycidyl ether, diepoxy ethylene glycol diglycidyl ether, resorcinol diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0060] In embodiments of the present invention, the curing agent comprises a compound having structure B, wherein structure B is:

[0061] ;

[0062] R1 represents one of H, C1-C12 alkyl, C1-C12 alkoxy, substituted aryl, unsubstituted aryl, substituted aryloxy, and unsubstituted aryloxy. This curing agent exhibits excellent compatibility with the matrix epoxy resin and can synergistically reduce the system's CTE. This invention achieves a significant reduction in CTE through resin system modification, curing agent optimization, and filler modification, while simultaneously maintaining mechanical properties and thermal stability, resulting in a chip-scale, one-component epoxy underfiller with low CTE, high Tg, balanced mechanical properties, and excellent filler dispersibility.

[0063] In an embodiment of the present invention, the amount of curing agent is: the ratio of the mass of curing agent to the molar amount of epoxy groups in the matrix epoxy resin is 38g~57g:1mol.

[0064] In an embodiment of the present invention, the chitosan-modified filler is obtained by mixing and pulverizing an inorganic filler with chitosan.

[0065] In embodiments of the present invention, the amount of chitosan-modified filler is 30-70 parts by weight (relative to 80-100 parts by weight of the matrix epoxy resin).

[0066] In an embodiment of the present invention, the mass ratio of inorganic filler to chitosan in the chitosan-modified filler is 7~15:1.

[0067] In embodiments of the present invention, the average molecular weight of chitosan in the chitosan-modified filler is 50kDa to 150kDa.

[0068] In an embodiment of the present invention, the raw materials of the low expansion coefficient chip-level single-component epoxy underfill adhesive also include 0-5 parts of dispersant, 0-2 parts of defoamer, and 0-2 parts of colorant.

[0069] In some embodiments of the present invention, the colorant is one or more of carbon black, iron oxide red, titanium dioxide, and phthalocyanine green.

[0070] In an embodiment of the present invention, the low expansion coefficient chip-level single-component epoxy underfill adhesive is made by uniformly mixing the raw materials.

[0071] In some embodiments of the present invention, the raw materials of the low expansion coefficient chip-level single-component epoxy underfill adhesive are mixed under vacuum conditions, and a curing agent is added last during mixing.

[0072] This invention also provides the application of the low expansion coefficient chip-grade single-component epoxy underfill adhesive in semiconductor chip packaging.

[0073] In embodiments of the present invention, it is used for chip-scale packaging (CSP) and / or flip-chip.

[0074] Example

[0075] The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available commercially or synthesized using conventional methods and are ready for use without further processing. Unless otherwise stated, all instruments used in the examples are available commercially.

[0076] The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available commercially or synthesized using conventional methods and are ready for use without further processing. Unless otherwise stated, all instruments used in the examples are available commercially.

[0077] (I) Chemical structure of anthracene-modified chitosan toughening agent

[0078] The chemical structure of the anthracene-modified chitosan toughening agent described in each embodiment and comparative example is as follows: based on chitosan, the hydrogen in the primary amine group is replaced by the group A2, so that the primary amine group forms a secondary amine group; the primary amine group to be replaced is all or part of the primary amine group in the chitosan.

[0079] The structure of the chitosan is as follows:

[0080] ;

[0081] Where n = 1~15;

[0082] The group A2 is

[0083] .

[0084] The anthracene-modified chitosan toughening agent can be prepared by the following reaction:

[0085] .

[0086] Taking chitosan with n=4 as an example, the specific preparation method is as follows:

[0087] Under a nitrogen atmosphere, anthracene-9-aldehyde (7 mmol) and chitosan (1 mmol) were added to a round-bottom flask equipped with a magnetic stirrer at a molar ratio of 7:1. Then, 30 mL of a dry tetrahydrofuran and methanol mixture was added. After the addition was complete, the mixture was refluxed at 70 °C and reacted for a certain period of time (6-8 h). The mixture was then cooled to room temperature, and sodium borohydride (25 mmol) was slowly added under an ice bath. After the addition was complete, the mixture was allowed to continue reacting at room temperature for a period of time (4-6 h).

[0088] After the reaction was completed by TLC monitoring, the pH of the reaction system was adjusted to 5-7 with dilute hydrochloric acid, filtered, and the resulting solid fraction was dried and purified by column chromatography (yield 40%).

[0089] The chemical structure of the obtained product was determined by testing and is as follows:

[0090] (abbreviated as TM1).

[0091] Figure 1 It's TM1. 1 H-NMR spectrum; 1H NMR (400 MHz, CDCl3): δ 8.45 (s, 1H), 8.39 (d,J = 9.99 Hz, 2H), 8.02 (d, J = 8.10 Hz,2H), 7.56 (t, J = 7.79 Hz, 2H), 7.49(t, J = 8.06 Hz, 2H), 5.63 (s, 2H), 1.90 (s, 1H), 1.64 (s, 1H), 1.27 (s, 2H), 0.89 (s, 1H), 0.10 (s, 1H) (ppm).

[0092] Figure 2 It's TM1. 13 C-NMR spectrum; 13 C NMR (100 MHz, CDCl3): δ 131.6, 131.1, 130.3,129.3, 128.5, 126.6, 125.2, 57.5, 29.8, 22.8, 14.3, 1.2, 0.1 (ppm).

[0093] (II) Preparation of curing agent

[0094] The curing agents in each embodiment can be prepared by reacting anthracene with an amino functional group. The specific preparation method is described below using TM2 as an example. The curing agents in this scheme have similar properties. Those skilled in the art, based on this and common knowledge, can use similar methods to prepare other curing agents in this scheme. The structural formula of TM2 is:

[0095] .

[0096] The reaction formula for preparing TM2 can be written as:

[0097] ;

[0098] The specific preparation method of TM2 is as follows:

[0099] (1) Dissolving the substrate: Add 10 mmol of anthracene to a dry flask, add 15 mL of glacial acetic acid, and stir to partially dissolve the anthracene; if the anthracene dissolves slowly in glacial acetic acid, heat to 30 °C to aid dissolution;

[0100] (2) Add dimethylamine: Slowly add a 40wt% dimethylamine aqueous solution (25mmol of dimethylamine). After stirring, the system will release heat and produce a small amount of smoke. Continue stirring for 10 minutes.

[0101] (3) Add formaldehyde: Cool the reaction solution to 30°C and slowly add a 37wt% formaldehyde aqueous solution (25mmol of formaldehyde). After the addition is complete, stir the reaction for 2 hours or let it stand for 4 hours to allow the reaction to proceed fully.

[0102] (4) Quenching and neutralization: Slowly pour the reaction solution into a beaker containing 100g of crushed ice, stir vigorously, and then slowly add a 30wt% sodium hydroxide aqueous solution until the pH of the system is 9~10. Keep the process at a low temperature to avoid product decomposition.

[0103] (5) Filtration and washing: The precipitated solid was filtered by Buchner funnel and washed with distilled water until the filtrate was neutral to obtain the crude solid product;

[0104] (6) Drying and recrystallization: The crude product was dried in a vacuum dryer (desiccant: anhydrous calcium chloride), and then dissolved in hot acetone. After cooling, needle-like crystals precipitated. After filtration, pure 1,4-bis(dimethylaminomethyl)anthracene was obtained.

[0105] Example 1

[0106] The low coefficient of thermal expansion chip-level single-component epoxy underfill adhesive of this embodiment comprises, by weight, the following raw materials:

[0107] Matrix epoxy resin: 95 parts of bisphenol F type epoxy resin and 5 parts of anthracene resin, totaling 100 parts;

[0108] Anthracene-modified chitosan toughening agent: n=5, R is methyl, R' is H, A2 group replaces hydrogen in 50% of primary amine groups; 8 parts;

[0109] Low viscosity epoxy resin: 5 parts neopentyl glycol diglycidyl ether;

[0110] Chitosan-modified filler: 30 parts of spherical silica and 3 parts of chitosan (average molecular weight 100kDa) were mixed in a ball mill for 2 hours and then pulverized by air jet milling (pressure 0.6MPa) to obtain a total of 33 parts;

[0111] Curing agent: The ratio of curing agent mass to the molar amount of epoxy groups in the matrix epoxy resin is 49.4 g : 1 mol; totaling 24.7 parts; the structure of the curing agent used is:

[0112] ;

[0113] Dispersant: FS-01, 0.5 parts; Defoamer: 2685, 0.5 parts; Pigment: Acetylene Black, 1 part.

[0114] This embodiment describes a method for preparing a low-expansion-coefficient chip-level single-component epoxy underfill adhesive:

[0115] (1) Add the matrix epoxy resin and low viscosity epoxy resin to the mixing tank, turn on the vacuum mode, heat to 120℃, rotate at 300rpm, and stir for 30min to make the system uniform.

[0116] (2) Add anthracene-modified chitosan toughening agent to the reactor, cool to 80°C, and stir at 300 rpm for 10 min;

[0117] (3) Cool down to 50°C, add chitosan-modified filler, colorant, dispersant and defoamer and stir for 10 minutes to ensure uniform dispersion of filler;

[0118] (4) Finally, add the curing agent, stir at 200 rpm for 5 min, and cool to room temperature to obtain chip-level single-component epoxy underfill adhesive.

[0119] Example 2

[0120] The low coefficient of thermal expansion chip-level single-component epoxy underfill adhesive of this embodiment comprises, by weight, the following raw materials:

[0121] Matrix epoxy resin: 90 parts of bisphenol A type epoxy resin and 10 parts of anthracene resin, totaling 100 parts;

[0122] Anthracene-modified chitosan toughening agent: n=10, R is phenoxy, R' is phenyl, and the A2 group replaces all hydrogen in the primary amine groups; 12 parts;

[0123] Low viscosity epoxy resin: 5 parts neopentyl glycol diglycidyl ether;

[0124] Chitosan-modified filler: 25 parts aluminum hydroxide and 3 parts chitosan (average molecular weight 100 kDa) were mixed in a ball mill for 3 hours and then pulverized by air jet milling (pressure 0.8 MPa) to obtain a total of 28 parts;

[0125] Curing agent: The ratio of curing agent mass to the molar amount of epoxy groups in the matrix epoxy resin is 47.5g:1mol; totaling 25 parts; the structure of the curing agent used is:

[0126] ;

[0127] Dispersant: FS-01, 0.5 parts; Defoamer: 2685, 0.5 parts; Pigment: Acetylene Black, 1 part.

[0128] This embodiment describes a method for preparing a low-expansion-coefficient chip-level single-component epoxy underfill adhesive:

[0129] (1) Add the matrix epoxy resin and low viscosity epoxy resin to the mixing tank, turn on the vacuum mode, heat to 120℃, rotate at 300rpm, and stir for 40min to make the system uniform.

[0130] (2) Add anthracene-modified chitosan toughening agent to the reactor, cool to 85°C, and stir at 300 rpm for 10 min;

[0131] (3) Cool down to 50°C, add chitosan-modified filler, colorant, dispersant and defoamer and stir for 10 minutes to ensure uniform dispersion of filler;

[0132] (4) Finally, add the curing agent, stir at 200 rpm for 5 min, and cool to room temperature to obtain chip-level single-component epoxy underfill adhesive.

[0133] Example 3

[0134] The low coefficient of thermal expansion chip-level single-component epoxy underfill adhesive of this embodiment comprises, by weight, the following raw materials:

[0135] Matrix epoxy resin: 85 parts of bisphenol F type epoxy resin and 15 parts of anthracene resin, totaling 100 parts;

[0136] Anthracene-modified chitosan toughening agent: n=15, R is C12 alkoxy, R' is C8 alkyl, A2 group replaces hydrogen in 80% of primary amine groups; 15 parts;

[0137] Low viscosity epoxy resin: 10 parts neopentyl glycol diglycidyl ether;

[0138] Chitosan-modified filler: 40 parts silica and 3 parts chitosan (average molecular weight 120 kDa) were mixed in a ball mill for 2.5 h and then pulverized by air jet milling (pressure 0.7 MPa); a total of 43 parts were obtained.

[0139] Curing agent: The ratio of curing agent mass to the molar amount of epoxy groups in the matrix epoxy resin is 51.3 g : 1 mol; totaling 27.5 parts; the structure of the curing agent used is:

[0140] In the formula, Ph refers to phenyl;

[0141] Dispersant: FS-01, 0.5 parts; Defoamer: 2685, 0.5 parts; Pigment: Acetylene Black, 1 part.

[0142] This embodiment describes a method for preparing a low-expansion-coefficient chip-level single-component epoxy underfill adhesive:

[0143] (1) Add the matrix epoxy resin and low viscosity epoxy resin to the mixing tank, turn on the vacuum mode, heat to 110℃, rotate at 500rpm, and stir for 40min to make the system uniform.

[0144] (2) Add anthracene-modified chitosan toughening agent to the reactor, cool to 85°C, and stir at 500 rpm for 10 min;

[0145] (3) Cool down to 50°C, add chitosan-modified filler, colorant, dispersant and defoamer and stir for 10 minutes to ensure uniform dispersion of filler;

[0146] (4) Finally, add the curing agent, stir at 180 rpm for 5 min, and cool to room temperature to obtain chip-level single-component epoxy underfill adhesive.

[0147] Comparative Example 1

[0148] This comparative example of a one-component epoxy underfill adhesive does not use anthracene-based resins; by weight, the raw materials include:

[0149] Matrix epoxy resin: 100 parts of bisphenol F type epoxy resin (anthracene-free resin); the ratio of curing agent mass to the molar amount of epoxy groups in the matrix epoxy resin is 49.4 g: 1 mol; other components are the same as in Example 1.

[0150] The preparation method of the comparative example single-component epoxy underfill adhesive is the same as that of Example 1.

[0151] Comparative Example 2

[0152] This comparative example of a one-component epoxy underfiller uses excessive amounts of anthracene-based resin; by weight, the raw materials include:

[0153] The matrix epoxy resin consists of 80 parts of bisphenol F type epoxy resin and 20 parts of anthracene resin, totaling 100 parts; the ratio of curing agent mass to the molar amount of epoxy groups in the matrix epoxy resin is 49.4 g: 1 mol; other components are the same as in Example 1.

[0154] The preparation method of the comparative example single-component epoxy underfill adhesive is the same as that of Example 1.

[0155] Comparative Example 3

[0156] The one-component epoxy underfill adhesive of this comparative example uses unmodified chitosan instead of anthracene-modified chitosan toughening agent; by weight, the raw materials include: 8 parts of chitosan with n=5; other components are the same as in Example 1.

[0157] The preparation method of this comparative example of a one-component epoxy underfiller differs from that of Example 1 only in that the chitosan is used instead of the anthracene-modified chitosan toughening agent.

[0158] Comparative Example 4

[0159] This comparative example uses a one-component epoxy underfill adhesive with a conventional polyetheramine curing agent; by weight, the raw materials include:

[0160] Curing agent: polyetheramine D230, the ratio of curing agent mass to the molar amount of epoxy groups in the matrix epoxy resin is 49.4 g: 1 mol; other components are the same as in Example 1.

[0161] The preparation method of the comparative example single-component epoxy underfill adhesive is the same as that of Example 1.

[0162] Comparative Example 5

[0163] The one-component epoxy underfiller in this comparative example uses unmodified filler instead of chitosan-modified filler. By weight, the raw materials include: 30 parts by weight of ball-milled spherical silica; other components are the same as in Example 1.

[0164] The preparation method of this comparative example of a one-component epoxy underfiller differs from that of Example 1 only in that pulverized silica is used instead of chitosan as a filler.

[0165] Detection and Analysis

[0166] Performance tests were conducted on various indicators of the single-component epoxy underfill adhesives of each embodiment and comparative example, as well as similar epoxy adhesive products on the market.

[0167] Curing method of each single-component epoxy underfill: Fill the mold with the underfill of each embodiment and comparative example, and heat-treat in a vacuum drying oven to achieve curing;

[0168] Comparative Example 4 used a traditional polyetheramine curing process: treatment at 80°C for 2 hours, followed by treatment at 120°C for 4 hours.

[0169] The curing process for other cases was as follows: 100°C for 2 hours, followed by 150°C for 4 hours, and then 180°C for 2 hours.

[0170] The cured samples were placed at room temperature (23~25℃) for 24 hours before testing.

[0171] The detection method is as follows:

[0172] Viscosity testing was performed according to GB / T 2794-2022 (replacing GB / T 2794-2013) using an NDJ-79 rotational viscometer at 23±0.5℃. After degassing the sample at room temperature for 24 hours, a suitable rotor and speed were matched, and the reading was taken after the reading stabilized. The test was repeated in triplicate, and the average value was taken.

[0173] Hardness testing was conducted according to GB / T 2411-2008, using a Shore D hardness tester to test the cured adhesive block (thickness ≥ 6 mm, with no gaps when insufficient). Five non-edge testing points were selected on the sample surface (spaced ≥ 10 mm apart). The reading was taken after the indenter was in contact for 15 seconds, and outliers were discarded and the average value was taken.

[0174] Tensile properties were determined according to GB / T 1040.2-2018. The specimens were Type I dumbbell-shaped (thickness 4±0.2 mm, width 10±0.2 mm, gauge length 50±0.5 mm). After conditioning at 23±2℃ and 50±10%RH for 16 hours, the specimens were stretched at a rate of 2 mm / min. The maximum load and elongation were recorded. Strength and elongation were calculated using the formulas, and the average of five parallel samples was taken.

[0175] The Tg test was conducted according to GB / T 40396-2021, using the DMA three-point bending mode. The sample was a 50mm×10mm×2mm cured adhesive strip, heated at 5℃ / min within the range of -80℃ to 200℃, and vibrated at 1Hz. The peak temperature of tanδ was taken as Tg.

[0176] CTE testing was conducted according to GB / T 36800.2-2018, using the TMA static compression mode to test a φ5mm×10mm cured adhesive column. The temperature was increased from -50℃ to 180℃ at a rate of 5℃ / min, with a load of 0.05N. The CTE in the glassy and rubbery states was calculated separately using α=ΔL / (L0×ΔT).

[0177] Thermal cycling was performed according to GB / T 2423.22-2022, testing the cast parts. The substrates were stainless steel boxes and copper blocks. Cycling procedure: -50℃ for 20 min → heating to 150℃ and holding for 20 min within 5 min → rapid cooling to -50℃ at a rate of ≥10℃ / min. Visual inspection was performed every 20 cycles. Cracks ≥2mm were considered failures. Five cast parts were tested in parallel for each sample group.

[0178] The test results are shown in Table 1.

[0179] Table 1. Performance test results of epoxy adhesives in each embodiment and comparative example, as well as commercially available products.

[0180]

[0181] As can be seen from the performance test results in Table 1, the single-component epoxy underfill adhesives of Examples 1-3 have low coefficients of thermal expansion and high Tg, and have significant advantages over commercially available products and comparative examples in terms of strength and resistance to thermal shock cycles.

[0182] Compared with the examples, Comparative Example 1 did not add anthracene resin, and the lack of a polycyclic rigid structure may lead to the inability to reduce the free volume of the system through the steric hindrance effect, making it difficult to reduce CTE, and the product has insufficient rigidity and thermal stability.

[0183] In Comparative Example 2, the amount of anthracene resin exceeded 15 wt%, resulting in a sharp increase in viscosity, which may lead to uneven dispersion, excessive crosslinking, internal stress, increased material brittleness, and decreased impact toughness.

[0184] In Comparative Example 3, the primary amine group of unmodified chitosan has low reactivity, which makes it unable to form a dense cross-linked network with epoxy resin, making it difficult to inhibit molecular chain movement and effectively reduce CTE. Furthermore, its interfacial compatibility with epoxy resin is insufficient, resulting in decreased material mechanical properties and poor resistance to thermal shock cycles.

[0185] The traditional polyetheramine curing agent used in Comparative Example 4 has poor compatibility with resin and filler, and cannot synergistically reduce CTE. Moreover, the cured material has a low Tg, and the molecular chain movement is intense at high temperature, resulting in a significantly higher CTE (especially below Tg) than the system of the present invention.

[0186] In Comparative Example 5, the unmodified filler tends to agglomerate and settle in the matrix epoxy resin, leading to an increase in internal defects, weak interfacial interaction, poor CTE reduction effect, and decreased mechanical properties (such as tensile strength).

Claims

1. A low coefficient of expansion, one-part epoxy underfill for chip scale packaging, characterized in that, By weight, the raw materials include: 80-100 parts of matrix epoxy resin, 5-15 parts of anthracene-modified chitosan toughening agent, and 2-10 parts of low-viscosity epoxy resin; it also includes chitosan-modified filler and curing agent. The matrix epoxy resin includes bisphenol-type epoxy resin and anthracene-based resin; the anthracene-based resin has an anthracene ring structure and accounts for 5wt%~15wt% of the matrix epoxy resin. The chemical structure of the anthracene-modified chitosan toughening agent is as follows: based on chitosan A1, the hydrogen in the primary amine group is replaced by group A2, so that the primary amine group forms a secondary amine group; the primary amine group to be replaced is all or part of the primary amine groups in chitosan A1; the structure of chitosan A1 is as follows: ； Where n = 1~15; said group A2 is ; Wherein R represents one of H, C1~C12 alkyl, C1~C12 alkoxy, substituted aryl, unsubstituted aryl, substituted aryloxy, and unsubstituted aryloxy. R' represents one of H, C1~C12 alkyl, substituted aryl, or unsubstituted aryl; represents a semi-bond; The curing agent includes a compound having structure B, wherein structure B is: ； Wherein R1 represents one of H, C1~C12 alkyl, C1~C12 alkoxy, substituted aryl, unsubstituted aryl, substituted aryloxy, and unsubstituted aryloxy.

2. The low CTE, one-part, epoxy underfill for chip scale packaging according to claim 1, wherein The bisphenol type epoxy resin includes one or more of bisphenol S type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, and linear phenolic epoxy resin. The low-viscosity epoxy resin includes one or more of the following: monoepoxy propenyl glycidyl ether, phenyl glycidyl ether, diepoxy ethylene glycol diglycidyl ether, resorcinol diglycidyl ether, and neopentyl glycol diglycidyl ether.

3. The low expansion coefficient chip-level one-component epoxy underfill adhesive according to claim 1, characterized in that, The amount of curing agent used is: the ratio of the mass of curing agent to the molar amount of epoxy groups in the matrix epoxy resin is 38g~57g:1mol.

4. The low CTE, one-part, epoxy underfill according to claim 1, wherein, The chitosan-modified filler is obtained by mixing and pulverizing inorganic fillers and chitosan.

5. The low coefficient of expansion, one-part epoxy underfill according to claim 1, wherein, The amount of chitosan-modified filler used is 30-70 parts; the mass ratio of inorganic filler to chitosan in the chitosan-modified filler is 7-15:1; the average molecular weight of chitosan in the chitosan-modified filler is 50kDa-150kDa.

6. The low coefficient of expansion, one-part, epoxy underfill according to claim 1, wherein, The raw materials for chip-grade single-component epoxy underfill adhesive with low expansion coefficient also include 0-5 parts dispersant, 0-2 parts defoamer, and 0-2 parts colorant.

7. The chip-level one-component epoxy underfiller with a low coefficient of thermal expansion according to any one of claims 1 to 6, characterized in that, The low expansion coefficient chip-grade single-component epoxy underfill is made by uniformly mixing all raw materials.

8. The application of the low coefficient of thermal expansion chip-grade single-component epoxy underfill as described in any one of claims 1 to 7 in semiconductor chip packaging.

9. Use of the low coefficient of expansion one-part epoxy underfill according to claim 8 in semiconductor chip packaging, characterized in that, Used for chip-scale packaging and / or flip-chip.

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