High-temperature-resistant conductive adhesive and preparation method thereof

Abstract

The invention relates to the technical field of conductive adhesives, and provides a high-temperature-resistant conductive adhesive and a preparation method thereof.The high-temperature-resistant conductive adhesive is prepared from, by weight, 5-30 parts of cyanate ester, 5-20 parts of bismaleimide, 5-10 parts of toughening modifier, 1-10 parts of catalyst, 60-90 parts of conductive filler, 1-10 parts of thixotropic agent and 1-10 parts of curing agent. According to the high-temperature-resistant conductive adhesive disclosed by the invention, through molecular structure design and multiphase composite toughening, the bottleneck that the mechanical property of the traditional conductive adhesive is suddenly reduced at high temperature is broken through. The BMI / CE copolymerization network provides a heat-resistant rigid framework, and the BA copolymerization dispersion phase absorbs stress to improve the adhesion, so that the balance between heat resistance and adhesion is realized. The technology provides a new-generation solution for high-end electronic packaging and high-temperature structure bonding, and has remarkable technical barriers and application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive adhesives, and in particular to a high-temperature resistant conductive adhesive and a preparation method thereof. Background Art

[0002] With the rapid development of electronic technology, the power and integration of semiconductor devices have continued to increase, placing higher demands on the performance of conductive adhesives. Conventional conductive adhesives, typically based on epoxy or acrylic resins, offer excellent mechanical properties and low volume resistivity, but their high-temperature resistance is poor. For example, under packaging conditions exceeding 200°C, the colloidal structure of conventional conductive adhesives easily decomposes, resulting in a decrease in mechanical properties and, in turn, causing reliability issues such as delamination from the chip or substrate and chip detachment. In certain specific applications, such as those requiring gold-tin solder sealing after chip bonding to meet low gas density requirements, the eutectic temperature of gold-tin solder can reach 280°C or even higher. Conventional epoxy conductive adhesives, however, cannot meet the requirements of high temperatures above 300°C and low gas production. Furthermore, the heat generated by semiconductor devices during operation continuously increases, and the long-term high-temperature operation of conductive adhesives accelerates the aging of the substrate, reducing the reliability and service life of the packaged device.

[0003] The patent with publication number CN116496751A mainly involves the copolymerization modification of cyanate ester and bismaleimide to prepare high-temperature resistant conductive adhesive. The patent aims to take into account the heat resistance and dielectric properties of the two. Its core solutions include: component design: cyanate ester resin (CE) and bismaleimide resin (BMI) are copolymerized to form a cross-linked network. Reaction mechanism: It relies on the -OCN group of cyanate ester and the maleimide cycloaddition reaction of BMI to generate a triazine ring and an imide cross-linked structure. Performance characteristics: High cross-linking density improves heat resistance and low dielectric loss, and is suitable for high-frequency wave-transparent materials (such as radar antenna covers and 5G substrates).

[0004] However, this system has certain drawbacks: BMI's highly cross-linked structure restricts the movement of molecular segments, leading to increased brittleness. The conductive adhesive's high brittleness and low toughness make it susceptible to brittle deformation when subjected to stress, accelerating the risk of crack initiation and thus accelerating bond failure and reducing adhesion. This is also the reason why, in patent publication number CN116496751A, a silicon chip bonded to a gold-plated substrate exhibits a maximum shear strength of only 22.79 MPa after curing. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one technical problem in the background technology and provide a high temperature resistant conductive adhesive and a preparation method thereof.

[0006] To achieve the above objectives, the present invention provides a high-temperature resistant conductive adhesive, which comprises, by weight, 5-30 parts of cyanate ester, 5-20 parts of bismaleimide, 5-10 parts of toughening modifier, 1-10 parts of catalyst, 60-90 parts of conductive filler, 1-10 parts of thixotropic agent, and 1-10 parts of curing agent.

[0007] According to one aspect of the present invention, the cyanate ester is one or more of bisphenol A cyanate, bisphenol B cyanate, bisphenol E cyanate, bisphenol F cyanate, bisphenol M cyanate, bisphenol AF cyanate, bisphenol AP cyanate, bisphenol BP cyanate, phenolic cyanate and dicyclopentadiene type cyanate.

[0008] According to one aspect of the present invention, the toughening modifier is allyl bisphenol A, allyl phenyl compound or allyl phenoloxy resin.

[0009] According to one aspect of the present invention, the catalyst is one or more diamine compounds selected from the group consisting of 4,4'-diaminodiphenyl sulfone, 3-ethynylaniline, diaminodiphenylmethane, 4,4'-diaminodiphenyl ether and 2-methylimidazole.

[0010] According to one aspect of the present invention, the conductive filler is one or more combinations of flaky silver powder, spherical silver powder, dendritic silver powder, flaky silver-coated copper powder, granular silver-coated copper powder and dendritic silver-coated copper powder.

[0011] According to one aspect of the present invention, the thixotropic agent is one or more of fumed silica, organic bentonite, hydrogenated castor oil, and polyamide wax.

[0012] According to one aspect of the present invention, the curing agent is one or more of nonylphenol, metal acetylacetonate and organotin.

[0013] In order to achieve the purpose of climbing the tree, the present invention also provides a method for preparing a high-temperature resistant conductive adhesive, comprising:

[0014] Cyanate, bismaleimide, toughening modifier and catalyst are added and mixed in sequence, and then heated and stirred to obtain a high temperature resistant resin.

[0015] The high-temperature resistant resin, conductive filler, thixotropic agent and curing agent are mixed evenly, and then subjected to three-roller grinding and planetary vacuum degassing treatment to obtain the high-temperature resistant conductive adhesive.

[0016] According to one aspect of the present invention, the heating and stirring conditions for heating and stirring a mixture of cyanate ester, bismaleimide, toughening modifier and catalyst to form a high temperature resistant resin are: 100-180° C. / 1-4 h.

[0017] According to one aspect of the present invention, the heating and stirring conditions for heating and stirring a mixture of cyanate ester, bismaleimide, toughening modifier and catalyst to form a high temperature resistant resin are: 120° C. / 2 h.

[0018] Compared with the existing technology, the present invention overcomes the technical bottleneck of not being able to achieve both high temperature resistance and bonding performance, and achieves the following beneficial effects:

[0019] Synergistic enhancement of high temperature resistance: The intrinsic heat resistance barrier of cyanate esters is difficult to withstand high temperatures above 300°C. The present invention significantly improves thermal stability by copolymerizing cyanate ester (CE) and bismaleimide (BMI) to form an interpenetrating network structure of triazine rings and imide rings. The thermal weight loss temperature of the modified resin reaches above 400°C, and the glass transition temperature (Tg) reaches 250°C, which is better than the traditional epoxy resin system. The high cross-linking density of BMI and the high heat resistance of CE work synergistically to give the material the ability to serve for a long time above 300°C.

[0020] Toughening and Adhesion Optimization: Allyl bisphenol A (BA) is copolymerized with bismaleimide (BMI) via an allyl group, introducing a flexible aliphatic long chain structure into the rigid backbone. This flexible segment effectively disperses stress concentration by adjusting the molecular chain conformation and absorbs impact energy through energy dissipation mechanisms such as molecular chain slippage, entanglement, and interlocking. This microstructural design significantly inhibits crack propagation, enabling the copolymer to achieve enhanced toughness while maintaining high strength, overcoming the brittle fracture characteristics of traditional cyanate ester resins.

[0021] This invention overcomes the bottleneck of traditional conductive adhesives, which suffer from a sharp drop in mechanical properties at high temperatures, through molecular structure design and multiphase composite toughening. The BMI / CE copolymer network provides a heat-resistant rigid backbone, while the BA copolymer dispersed phase absorbs stress and improves adhesion, achieving a balance between heat resistance and adhesion. This technology offers a next-generation solution for high-end electronic packaging and high-temperature structural bonding, with significant technical barriers and promising applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The flowchart schematically shows a method for preparing a high temperature resistant conductive adhesive according to one embodiment of the present invention. DETAILED DESCRIPTION

[0023] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only intended to enable those skilled in the art to better understand and implement the present invention, rather than to imply any limitation on the scope of the present invention.

[0024] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including, but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment."

[0025] To achieve the above objectives, the present invention provides a high-temperature resistant conductive adhesive, which comprises, by weight, 5-30 parts of cyanate ester, 5-20 parts of bismaleimide, 5-10 parts of toughening modifier, 1-10 parts of catalyst, 60-90 parts of conductive filler, 1-10 parts of thixotropic agent, and 1-10 parts of curing agent.

[0026] Further, according to one embodiment of the present invention, the cyanate ester is one or more of bisphenol A cyanate, bisphenol B cyanate, bisphenol E cyanate, bisphenol F cyanate, bisphenol M cyanate, bisphenol AF cyanate, bisphenol AP cyanate, bisphenol BP cyanate, phenolic cyanate and dicyclopentadiene type cyanate.

[0027] Further, according to one embodiment of the present invention, the toughening modifier is allyl bisphenol A, allyl phenyl compound or allyl phenoloxy resin.

[0028] Furthermore, according to one embodiment of the present invention, the catalyst is one or more diamine compounds selected from the group consisting of 4,4'-diaminodiphenyl sulfone, 3-ethynylaniline, diaminodiphenylmethane, 4,4'-diaminodiphenyl ether and 2-methylimidazole.

[0029] Furthermore, according to one embodiment of the present invention, the conductive filler is one or more combinations of flaky silver powder, spherical silver powder, dendritic silver powder, flaky silver-coated copper powder, granular silver-coated copper powder and dendritic silver-coated copper powder.

[0030] Furthermore, according to one embodiment of the present invention, the thixotropic agent is one or more of fumed silica, organic bentonite, hydrogenated castor oil, and polyamide wax.

[0031] Further, according to one embodiment of the present invention, the curing agent is one or more of nonylphenol, metal acetylacetonate and organotin.

[0032] Furthermore, in order to achieve the above object, the present invention also provides a method for preparing a high temperature resistant conductive adhesive, such as Figure 1 Shown, including:

[0033] Cyanate, bismaleimide, toughening modifier and catalyst are added and mixed in sequence, and then heated and stirred to obtain a high temperature resistant resin.

[0034] The high-temperature resistant resin, conductive filler, thixotropic agent and curing agent are mixed evenly, and then subjected to three-roller grinding and planetary vacuum degassing treatment to obtain the high-temperature resistant conductive adhesive.

[0035] Furthermore, according to one embodiment of the present invention, the heating and stirring conditions for heating and stirring the mixture of cyanate ester, bismaleimide, toughening modifier and catalyst to form the high temperature resistant resin are: 100-180° C. / 1-4 h.

[0036] Preferably, the heating and stirring conditions for heating and stirring the mixture of cyanate ester, bismaleimide, toughening modifier and catalyst to form the high temperature resistant resin are: 120° C. / 2 h.

[0037] According to the above scheme of the present invention, the present invention adopts a chemical copolymerization toughening modification strategy to construct a "rigid-semi-rigid-flexible" ternary multi-scale synergistic cross-linked network structure of cyanate resin, bismaleimide resin (bismaleimide resin) and allyl bisphenol A. Specifically, it is manifested as follows: a. Cyanate resin, with its excellent heat resistance and thermal stability as the matrix, provides a high-strength and high-modulus skeleton structure, ensuring the dimensional stability and mechanical properties of the material in a high-temperature environment; b. Bismaleimide resin has good heat resistance and chemical stability, which can further enhance the heat resistance of the system; c. Allyl bisphenol A is an active monomer. Its introduction can not only effectively improve the fluidity of the resin system, but also form a network structure with cyanate resin and bismaleimide resin by chemical bonding, thereby significantly improving the toughness of the material without significantly reducing the heat resistance.

[0038] By precisely controlling the ratio of the ternary resins and the copolymerization reaction conditions, they achieved uniform dispersion and effective crosslinking of the molecular segments of the cyanate ester resin, bismaleimide resin, and allyl bisphenol A, successfully constructing a new high-temperature conductive adhesive material system that combines high heat resistance with excellent toughness. This system overcomes the technical bottleneck of traditional high-temperature conductive adhesives, which often suffer from a trade-off between heat resistance and adhesion. It provides a new approach and technical path for the development of high-performance, high-temperature conductive adhesives and is expected to find widespread application in fields with extremely demanding material performance requirements, such as aerospace and electronic packaging.

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clear, the effects that can be achieved by the present invention are further described in detail below in combination with embodiments and comparative examples. It should be understood that the specific embodiment described here is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] Material preparation: 5g bisphenol E cyanate, 5g bismaleimide, 5g allyl bisphenol A, 1g 4,4'-diaminodiphenyl sulfone, 60g flake silver powder, 1g fumed silica, and 1g acetylacetonate.

[0042] The preparation process and steps are as follows:

[0043] The specified mass of bisphenol E cyanate, bismaleimide, allyl bisphenol A, and 4,4'-diaminodiphenyl sulfone in the above raw material formula were added and mixed in sequence, and stirred and mixed evenly at 120°C / 2h to obtain a high temperature resistant resin;

[0044] The high-temperature resistant resin, flaky silver powder, fumed silica, and acetylacetonate in the above-mentioned prescribed mass parts are mixed evenly and then subjected to three-roller grinding, planetary vacuum degassing and other processes to obtain a high-bonding strength high-temperature resistant conductive adhesive.

[0045] Example 2:

[0046] The difference from Example 1 is that the amount of bisphenol E cyanate is 15 g.

[0047] Example 3:

[0048] The difference from Example 1 is that the cyanate ester is bisphenol A cyanate.

[0049] Example 4:

[0050] The difference from Example 3 is that the amount of bisphenol A cyanate is 15 g.

[0051] Example 5:

[0052] The difference from Example 1 is that the cyanate ester is bisphenol AP cyanate.

[0053] Example 6:

[0054] The difference from Example 5 is that the amount of bisphenol AP cyanate is 30 g.

[0055] Example 7:

[0056] The difference from Example 1 is that the amount of allyl bisphenol A is 8 g.

[0057] Example 8:

[0058] The difference from Example 1 is that the toughening modifier is allyl phenol oxide resin.

[0059] Example 9:

[0060] The difference from Example 8 is that the amount of allylphenoloxy resin is 10 g.

[0061] Example 10:

[0062] The difference from Example 1 is that the amount of 4,4'-diaminodiphenyl sulfone is 8 g.

[0063] Example 11:

[0064] The difference from Example 1 is that the catalyst is 4,4'-diaminodiphenyl ether.

[0065] Example 12:

[0066] The difference from Example 11 is that the amount of 4,4'-diaminodiphenyl ether is 10 g.

[0067] Example 13:

[0068] The difference from Example 1 is that the amount of flaky silver powder is 90 g.

[0069] Example 14:

[0070] The difference from Example 1 is that the conductive filler is flaky silver-coated copper powder.

[0071] Example 15:

[0072] The difference from Example 14 is that the amount of flaky silver-coated copper powder is 80 g.

[0073] Example 16:

[0074] The difference from Example 1 is that the conductive filler is dendritic silver-coated copper powder.

[0075] Example 17:

[0076] The difference from Example 16 is that the amount of dendritic silver-coated copper powder is 75 g.

[0077] Example 18:

[0078] The difference from Example 1 is that 8 g of fumed silica was used.

[0079] Example 19:

[0080] The difference from Example 1 is that the thixotropic agent is organic bentonite.

[0081] Example 20:

[0082] The difference from Example 19 is that the amount of organobentonite is 10 g.

[0083] Example 21:

[0084] The difference from Example 1 is that the amount of acetylacetonate is 10 g.

[0085] Example 22:

[0086] The difference from Example 1 is that the curing agent is nonylphenol.

[0087] Example 23:

[0088] The difference from Example 22 is that the amount of nonylphenol is 8 g.

[0089] Example 24:

[0090] The difference from Example 1 is that the amount of bismaleimide is 10 g.

[0091] Example 25:

[0092] The difference from Example 1 is that the amount of bismaleimide is 20 g.

[0093] Example 26:

[0094] The difference from Example 1 is that the heating and stirring conditions are 100° C. / 4 h.

[0095] Example 27:

[0096] The difference from Example 1 is that the heating and stirring conditions are 180° C. / 1 h.

[0097] Comparative Example 1: To verify the technical effects of the present invention, this comparative example selected a method for preparing a conductive adhesive without adding allyl bisphenol A. Specifically, the following materials were prepared: 5g of bisphenol E cyanate, 5g of bismaleimide, 1g of 4,4'-diaminodiphenyl sulfone, 60g of flaky silver powder, 1g of fumed silica, and 1g of acetylacetonate.

[0098] The preparation process and steps are as follows: bisphenol E cyanate, bismaleimide, allyl bisphenol A, and 4,4'-diaminodiphenyl sulfone in the above raw material formula are added in sequence, and stirred and mixed evenly at 120°C / 2h to obtain a high-temperature resistant resin; the above-mentioned high-temperature resistant resin, flaky silver powder, fumed silica, and acetylacetonate in the specified mass parts are mixed evenly, and then subjected to three-roll grinding, planetary vacuum degassing and other processes to obtain a high-temperature resistant conductive adhesive.

[0099] The following performance tests were performed on some of the above examples and comparative examples:

[0100] Thermogravimetric analysis: According to the method specified in GJB548C-2021, a small amount of sample was taken after curing and the thermal weight loss was tested using a thermogravimetric analyzer (nitrogen atmosphere, heating from room temperature to 400°C at a rate of 10K / min).

[0101] Chip shear strength: measured according to GJB548C-2021 method 2019.3 (silicon-based 2×2 mm chip, gold-plated Kovar substrate) (MPa).

[0102] Volume resistivity: measured according to GJB548C-2021 method 5011.

[0103] Glass transition temperature: GB / T 19466.2-2004 Plastics Differential Scanning Calorimetry (DSC) Part 2: Determination of glass transition temperature (nitrogen atmosphere, heating from room temperature to 300°C at a rate of 10 K / min).

[0104] The key performance indicators of the high-temperature conductive adhesives prepared in all the above examples were met: chip shear strength ≥ 75 MPa; thermal weight loss ≤ 0.2% at 340°C and ≤ 0.3% at 400°C; glass transition temperature ≥ 240°C; and volume resistivity ≤ 10-2 Ω·cm. The conductive adhesives from some examples and comparative examples were subjected to the aforementioned performance tests and analyzed and compared. The results are shown in Table 1.

[0105] Table 1 Performance parameters of conductive adhesives in various embodiments and comparative examples

[0106]

[0107] As shown in Table 1, the experimental results clearly show that the introduction of allyl bisphenol A plays an extremely critical role in improving the bonding performance of high-temperature resistant conductive adhesive, and its adhesion is improved by as much as about 600%. More significantly, compared with the traditional solution, the high-temperature resistant conductive adhesive of the present invention has achieved a substantial improvement of about 350% in adhesion. This result fully confirms that the technical solution of the present invention can significantly enhance the bonding performance while ensuring excellent heat resistance, thereby achieving simultaneous optimization of heat resistance and adhesion in the field of high-temperature resistant conductive adhesives. This not only provides a more reliable solution for high-temperature resistant packaging applications with high requirements such as gold-tin sealing, but also highlights the great significance of the present invention in terms of technological innovation and practical application value.

[0108] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. High temperature resistant conductive adhesive, characterized in that: The high-temperature resistant conductive adhesive comprises, by weight, 5-30 parts of cyanate ester, 5-20 parts of bismaleimide, 5-10 parts of toughening modifier, 1-10 parts of catalyst, 60-90 parts of conductive filler, 1-10 parts of thixotropic agent, and 1-10 parts of curing agent.

2. The high temperature resistant conductive adhesive according to claim 1, characterized in that: The cyanate ester is one or more of bisphenol A cyanate, bisphenol B cyanate, bisphenol E cyanate, bisphenol F cyanate, bisphenol M cyanate, bisphenol AF cyanate, bisphenol AP cyanate, bisphenol BP cyanate, phenolic cyanate and dicyclopentadiene type cyanate.

3. The high temperature resistant conductive adhesive according to claim 1, characterized in that: The toughening modifier is allyl bisphenol A, allyl phenyl compound or allyl phenol oxide resin.

4. The high temperature resistant conductive adhesive according to claim 1, characterized in that: The catalyst is one or more diamine compounds such as 4,4'-diaminodiphenyl sulfone, 3-ethynylaniline, diaminodiphenylmethane, 4,4'-diaminodiphenyl ether and 2-methylimidazole.

5. The high temperature resistant conductive adhesive according to claim 1, characterized in that: The conductive filler is one or more combinations of flaky silver powder, spherical silver powder, dendritic silver powder, flaky silver-coated copper powder, granular silver-coated copper powder and dendritic silver-coated copper powder.

6. The high temperature resistant conductive adhesive according to claim 1, characterized in that: The thixotropic agent is one or more of fumed silica, organic bentonite, hydrogenated castor oil, and polyamide wax.

7. The high temperature resistant conductive adhesive according to any one of claims 1 to 6, characterized in that: The curing agent is one or more of nonylphenol, metal acetylacetonate and organotin.

8. The method for preparing a high temperature resistant conductive adhesive according to any one of claims 1 to 7, characterized in that: include: Cyanate, bismaleimide, toughening modifier and catalyst are added and mixed in sequence, and then heated and stirred to obtain a high temperature resistant resin. The high-temperature resistant resin, conductive filler, thixotropic agent and curing agent are mixed evenly, and then subjected to three-roller grinding and planetary vacuum degassing treatment to obtain the high-temperature resistant conductive adhesive.

9. The method for preparing a high temperature resistant conductive adhesive according to claim 8, characterized in that: The heating and stirring conditions for heating and stirring the mixture of cyanate ester, bismaleimide, toughening modifier and catalyst to form high temperature resistant resin are: 100-180℃ / 1-4h.

10. The method for preparing a high temperature resistant conductive adhesive according to claim 9, characterized in that: The heating and stirring conditions for heating and stirring the mixture of cyanate ester, bismaleimide, toughening modifier and catalyst to form high temperature resistant resin are: 120° C. / 2 h.

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