Preparation method of single-component epoxy electronic glue with low leveling property and low curing shrinkage

Abstract

The invention relates to a preparation method of a single-component epoxy electronic adhesive with low leveling property and low curing shrinkage. The epoxy electronic adhesive is prepared by ball-milling epoxy resin, a high-flexibility reactive flexibilizer, an auxiliary binder, a hydrophobic filler, a latent curing agent and a curing accelerator and then curing under temperature gradient. According to the method, the epoxy electronic glue with single-component stability, low leveling characteristic and low curing shrinkage rate can be prepared, and the performance requirements of high-density and miniaturized electronic packaging on precision, precision and fineness are met.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductors, in particular to a preparation method of a single-component low-flowing low-curing shrinkage epoxy electronic adhesive. BACKGROUND

[0002] In integrated circuits, the failure of material interfaces (such as chips and lead frames, gold wires and solder joints, packages and substrates) is a common source of failure. Epoxy resin, with its high bonding strength, low curing shrinkage, and high temperature resistance, has become the most core packaging / bonding material in the microelectronics industry.

[0003] Epoxy resin, with its strong adhesion due to high polarity epoxy groups and low curing shrinkage, can effectively combine heterogeneous materials into a whole, resist thermal stress and mechanical impact, and maintain structural stability in high temperature environments, thus meeting the requirements of traditional integrated circuit packaging for strength, precision and heat resistance. However, with the further development of electronic devices towards ultra-high density, miniaturization and high reliability, the problems of excessive infiltration and curing shrinkage of existing epoxy electronic adhesives have become increasingly prominent, which can easily lead to component misalignment and performance degradation.

[0004] In view of the above problems, the prior art has made improvement attempts. Patent CN120795845A discloses a single-component low-viscosity non-glue-overflowing epoxy resin electronic adhesive and a preparation method thereof, which solves the problems of glue drawing, temperature rising and glue overflow by adding a thermoplastic resin (such as polyvinyl butyral ester, phenoxy resin, etc.) to the epoxy resin. However, the patent does not mention the molecular weight of the selected thermoplastic resin, because glue drawing is not only related to the viscosity of the glue, but also greatly related to the molecular weight of the materials in the system; at the same time, the patent also does not mention the reason for the glue overflow of the thermoplastic resin glue body after heating, in theory, the above thermoplastic resin cannot form a crosslinked network structure with the epoxy resin, and increasing the temperature will increase the flowability of the thermoplastic resin, which is more likely to cause glue overflow, and even the imbalance of system compatibility can also cause the phenomenon of glue layering. The fillers used in the patent are one or a combination of at least two of nano calcium carbonate, diatomite, montmorillonite, silicon powder and carbon black. Currently, nano calcium carbonate, silicon powder and carbon black exist in two categories of hydrophilic and hydrophobic. Different types of fillers have a great influence on glue overflow and even the wettability of electronic materials. SUMMARY

[0005] In order to solve the above-mentioned problems, the purpose of the present application is to provide a preparation method of a single-component low-flowing low-curing shrinkage epoxy electronic adhesive, which can effectively control the flow and capillary infiltration phenomena of the glue after dispensing, and significantly reduce the curing shrinkage rate, and better meet the performance requirements of precise, accurate and fine packaging of electronic products.

[0006] To this end, the application provides a preparation method of a single-component low-flowing low-curing shrinkage epoxy electronic adhesive, comprising:

[0007] A preparation method of a single-component low-flowing low-curing shrinkage epoxy electronic adhesive, characterized in that the epoxy electronic adhesive is prepared by ball milling epoxy resin, high-flexibility reactive toughening agent, adhesion aid, hydrophobic filler, latent curing agent and curing accelerator and then curing under a temperature gradient; wherein the latent curing agent is one or more of boron trifluoride-monoethylamine complex, modified imidazole, dicyandiamide, modified dicyandiamide, ketimine, aldimine, iodonium salt and sulfonium salt; the high-flexibility reactive toughening agent is one or more of carboxyl-terminated butyl nitrile rubber (CTBN), amino-terminated butyl nitrile rubber (ATBN), hydroxyl-terminated butyl nitrile rubber (HTBN), polyethylene glycol, hydroxyl-terminated polyester and hydroxyl-containing polyacrylate; and the hydrophobic filler is one or more of hydrophobic nano calcium carbonate, hydrophobic fumed silica, hydrophobic carbon black and hydrophobic titanium dioxide.

[0008] In some embodiments, the method comprises the following steps:

[0009] S1, mixing the epoxy resin, high-flexibility reactive toughening agent and adhesion aid according to a mass ratio of 1:(0.05-0.3):(0.01-0.05), ball milling at 100-200 rpm for 2-4 h to form a mixed resin A;

[0010] S2, adding the hydrophobic filler to the mixed resin A according to a mass ratio of epoxy resin 1:hydrophobic filler (0.5-5), ball milling at 100-200 rpm for 4-8 h to form a mixed resin B;

[0011] S3, adding the latent curing agent and curing accelerator to the mixed resin B according to a mass ratio of epoxy resin 1:latent curing agent (0.1-0.3):curing accelerator (0.01-0.1), ball milling at 100-200 rpm for 1-2 h to obtain the epoxy electronic adhesive.

[0012] In some embodiments, the latent curing agent is one or more of modified imidazole and modified dicyandiamide.

[0013] In some embodiments, the high-flexibility reactive toughening agent is hydroxyl-terminated butyl nitrile rubber.

[0014] In some embodiments, the number average molecular weight of the hydroxyl-terminated butyl nitrile rubber is 1500-4000 g / mol.

[0015] In some embodiments, the hydrophobic filler is one or more of hydrophobic fumed silica and hydrophobic carbon black.

[0016] In some embodiments, the epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, phenol-aldehyde epoxy resin, alicyclic epoxy resin, hydrogenated bisphenol A epoxy resin.

[0017] In some embodiments, the adhesion promoter is one or more of amino silane coupling agent (KH550), epoxy silane coupling agent (KH560), methacryloxy silane coupling agent, titanate coupling agent.

[0018] In some embodiments, the curing accelerator is one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 4-chlorophenyl-N,N-dimethylurea, benzyl dimethyl amine (BDMA), triethanolamine, tris(dimethylaminomethyl)phenol, benzyltriethylammonium chloride, tetrabutylammonium bromide.

[0019] Compared with the prior art, the application has the following advantages:

[0020] By selecting a latent curing agent, the electronic adhesive is single-component curable; by selecting a hydrophobic filler, the electronic adhesive has no leveling phenomenon on the substrate, electronic components, electrodes and other materials, solving the problem of performance degradation of conventional epoxy electronic adhesive due to leveling and capillary infiltration; by selecting a high-softness reactive toughening agent, the curing shrinkage rate of the electronic adhesive is reduced, solving the problem of excessive displacement of electronic components caused by high curing shrinkage rate of conventional epoxy electronic adhesive, and better meeting the performance requirements of precise, accurate and fine packaging of electronic products. DETAILED DESCRIPTION

[0021] To describe the technical content, structural features, purposes and effects of the application in detail, the technical solutions in the embodiments of the application will be described below in combination with the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. In the following description, for the purpose of explanation, many specific details are set forth in order to provide a thorough understanding of various exemplary embodiments or implementations of the application. However, various exemplary embodiments can also be implemented without these specific details or in one or more equivalent arrangements. In addition, various exemplary embodiments can be different, but not necessarily exclusive. For example, the specific shape, structure and characteristics of an exemplary embodiment can be used or implemented in another exemplary embodiment without departing from the inventive concept.

[0022] Hereinafter, the terms "first", "second", and the like are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0023] The epoxy resin can achieve excellent wetting and mechanical interlocking in integrated circuits due to its highly polar epoxy group, forming a high-strength "riveting" structure that effectively resists thermal stress and mechanical impact; its low curing shrinkage protects the structural integrity of micron-level precision, while the highly cross-linked benzene ring structure endows it with the ability to work stably at high temperatures for a long time. However, traditional epoxy electronic adhesives still have limitations when dealing with ultra-high density and miniaturized packaging requirements: first, it is difficult to balance storage stability and curing efficiency, and single-component systems often face the contradiction between curing speed and shelf life; second, the glue is prone to excessive leveling and capillary penetration, affecting the packaging position accuracy and possibly causing electrical failure; third, residual curing shrinkage stress may still cause micro-device displacement, restricting packaging reliability and yield.

[0024] It is found through research that latent curing agents can achieve long-term stable storage of electronic adhesives under single-component conditions, and rapidly trigger curing reactions after heating, thereby effectively balancing storage and process efficiency; the addition of hydrophobic fillers can significantly adjust the surface energy of the system, inhibit the spreading and penetration of the glue on the surface of the substrate and components, and ensure precise and controllable glue shape; the use of high- flexibility reactive toughening agents that can participate in the reaction introduces flexible segments into the cross-linked network, which can absorb and disperse curing stress, significantly reduce the volume shrinkage rate, and avoid micro-displacement caused by shrinkage. The synergistic effect of the above three key components and epoxy resin systematically makes up for the deficiencies of traditional epoxy resins in excessive wetting and curing shrinkage of electronic materials, better meeting the more precise, accurate and fine needs of electronic products.

[0025] Accordingly, the present application proposes a preparation method of a single-component low-flowing low-curing shrinkage epoxy electronic adhesive, comprising: the epoxy electronic adhesive is prepared by grinding epoxy resin, high-flexibility reactive toughening agent, adhesion aid, hydrophobic filler, latent curing agent and curing accelerator at a temperature gradient of 80℃ for 1h, 100℃ for 1h and 120℃ for 1h;

[0026] In the present embodiment, the epoxy resin, the high-flexibility reactive toughening agent, and the adhesion promoter are mixed in a mass ratio of 1 :(0.05-0.3):(0.01-0.05), and after ball milling at 100-200 rpm for 2-4 h, a mixed resin A is formed; the hydrophobic filler is added to the mixed resin A in a mass ratio of 1 :(0.5-5) between the epoxy resin and the hydrophobic filler, and after ball milling at 100-200 rpm for 4-8 h, a mixed resin B is formed; the latent curing agent and the curing accelerator are added to the mixed resin B in a mass ratio of 1 :(0.1-0.3):(0.01-0.1) between the epoxy resin, the latent curing agent, and the curing accelerator, and after ball milling at 100-200 rpm for 1-2 h, a single-component epoxy electronic adhesive with low flow leveling and low curing shrinkage is prepared.

[0027] The epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin, and hydrogenated bisphenol A type epoxy resin. In the present embodiment, the epoxy resin is bisphenol A type, in particular, two kinds of epoxy resins of E-51 and E-44 in bisphenol A.

[0028] The high-flexibility reactive toughening agent is one or more of carboxyl-terminated butyl nitrile rubber (CTBN), amino-terminated butyl nitrile rubber (ATBN), hydroxyl-terminated butyl nitrile rubber (HTBN), polyethylene glycol, hydroxyl-containing polyester, and hydroxyl-containing polyacrylate. In the present embodiment, the high-flexibility reactive toughening agent is HTBN, and the number average molecular weight of the HTBN is 1500-4000 g / mol. The function of the high-flexibility reactive toughening agent is to reduce the curing shrinkage of the electronic adhesive, and to solve the problem of excessive displacement of electronic components caused by high curing shrinkage of conventional epoxy electronic adhesives.

[0029] The adhesion promoter is one or more of amino silane coupling agent (KH550), epoxy silane coupling agent (KH560), methacryloyloxy silane coupling agent, and titanate coupling agent. In the present embodiment, the adhesion promoter is one or more of KH550 and KH560.

[0030] The hydrophobic filler is one or more of hydrophobic nano calcium carbonate, hydrophobic fumed silica, hydrophobic carbon black, and hydrophobic titanium white powder. In the present embodiment, the hydrophobic filler is one or more of hydrophobic fumed silica and hydrophobic carbon black. The function of the hydrophobic filler is to make the electronic adhesive have no flow leveling phenomenon on materials such as substrates, electronic components, and electrodes, and to solve the problem of performance degradation of electronic products caused by flow leveling and capillary wetting of conventional epoxy electronic adhesives.

[0031] The latent curing agent is one or more of boron trifluoride-monoethylamine complex, modified imidazole, dicyandiamide and modified dicyandiamide, ketimine, aldimine, iodonium salt, and sulfonium salt. In the present embodiment, the latent curing agent is one or more of modified imidazole and modified dicyandiamide. The function of the latent curing agent is to make the electronic adhesive single-component curable.

[0032] The curing accelerator is one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 4-chlorophenyl-N,N-dimethylurea, benzyl dimethyl amine (BDMA), triethanolamine, tris(dimethylaminomethyl)phenol, benzyltriethylammonium chloride, tetrabutylammonium bromide. In this embodiment, the curing accelerator is 2-ethyl-4-methylimidazole and 3-(3,4-dichlorophenyl)-1,1-dimethylurea.

[0033] The following examples and comparative examples verify the leveling property and the curing shrinkage of the epoxy electronic adhesive based on the above preparation method. The leveling property is manifested by the maximum diameter of the epoxy adhesive before and after curing.

[0034] In Example 1 of the present application,

[0035] 100 g of E-44 epoxy resin, 20 g of HTBN (number average molecular weight of 2000 g / mol), and 2 g of KH550 were weighed and ball-milled at a speed of 150 rpm for 3 h to obtain epoxy resin mixture A.

[0036] 200 g of hydrophobic fumed silica was added to the epoxy resin mixture A and ball-milled at a speed of 150 rpm for 6 h to obtain epoxy resin mixture B.

[0037] 20 g of modified dicyandiamide and 2 g of 3-(3,4-dichlorophenyl)-1,1-dimethylurea were added to the epoxy resin mixture B and ball-milled at a speed of 150 rpm for 1 h to obtain the epoxy adhesive.

[0038] The epoxy adhesive was cured at a temperature gradient of 80°C for 1 h, 100°C for 1 h, and 120°C for 1 h to obtain the epoxy electronic adhesive.

[0039] In Example 2 of the present application,

[0040] 100 g of E-51 epoxy resin, 10 g of HTBN (number average molecular weight of 1500 g / mol), and 5 g of KH560 were weighed and ball-milled at a speed of 150 rpm for 4 h to obtain epoxy resin mixture A.

[0041] 200 g of hydrophobic carbon black was added to the epoxy resin mixture A and ball-milled at a speed of 150 rpm for 5 h to obtain epoxy resin mixture B.

[0042] 25 g of modified imidazole and 2 g of 2-ethyl-4-methylimidazole were added to the epoxy resin mixture B and ball-milled at a speed of 150 rpm for 2 h to obtain the epoxy adhesive.

[0043] The epoxy glue is cured at a temperature gradient of 80°C for 1 h, 100°C for 1 h, and 120°C for 1 h to obtain an epoxy electronic glue.

[0044] In the present application comparative example 1,

[0045] 100 g of E-51 epoxy resin, 20 g of polyethylene glycol (number average molecular weight of 2000 g / mol), and 2 g of methacryloxy silane coupling agent were weighed out, ball-milled at a speed of 150 rpm for 3 h to obtain epoxy mixed resin A.

[0046] 200 g of hydrophilic fumed silica A-380 was added to the epoxy mixed resin A, and ball-milled at a speed of 150 rpm for 6 h to obtain epoxy mixed resin B.

[0047] 20 g of boron trifluoride-monoethylamine complex and 2 g of 2-methylimidazole were added to the epoxy mixed resin B, and ball-milled at a speed of 150 rpm for 1 h to obtain an epoxy glue.

[0048] The epoxy glue was cured at a temperature gradient of 80°C for 1 h, 100°C for 1 h, and 120°C for 1 h to obtain an epoxy electronic glue.

[0049] In the present application comparative example 2,

[0050] 100 g of E-44 epoxy resin, 10 g of low molecular polyethylene (number average molecular weight of 5000 g / mol), and 1 g of titanate coupling agent were weighed out, ball-milled at a speed of 150 rpm for 2 h to obtain epoxy mixed resin A.

[0051] 100 g of hydrophilic carbon black was added to the epoxy mixed resin A, and ball-milled at a speed of 150 rpm for 4 h to obtain epoxy mixed resin B.

[0052] 15 g of modified dicyandiamide and 5 g of tris(dimethylaminomethyl)phenol were added to the epoxy mixed resin B, and ball-milled at a speed of 150 rpm for 2 h to obtain an epoxy glue.

[0053] The epoxy glue was cured at a temperature gradient of 80°C for 1 h, 100°C for 1 h, and 120°C for 1 h to obtain an epoxy electronic glue.

[0054] The experimental data are shown in the following table:

[0055] maximum diameter before and after curing curing shrinkage example 1 15％ 0.5％ example 2 30％ 0.7％ comparative example 1 135％ 2.7％ comparative example 2 160％ 2.3％

[0056] From the above table, it can be seen that the filler in Comparative Example 1 is hydrophilic fumed silica A-380, and the toughening agent in Comparative Example 2 is low molecular polyethylene. The maximum diameter increase rate of the colloids in both Comparative Examples before and after curing is more than 100%, indicating that there is a significant leveling and spreading phenomenon. The epoxy electronic adhesive system described in the present application is a single-component system. The components are mixed by ball milling and stored at room temperature, and no on-site preparation is required for direct dispensing. The maximum diameter increase rate of the colloids before and after curing is controlled to be within 30%, indicating that the colloids have no significant leveling and capillary infiltration behavior after application, and the shape is well maintained. At the same time, the curing shrinkage of the colloids is not more than 0.7%, which is significantly lower than the shrinkage level of conventional epoxy systems. Therefore, by using a latent curing agent, a hydrophobic filler, and a high- flexibility reactive toughening agent, an epoxy electronic adhesive with single-component stability, low leveling properties, and low curing shrinkage can be successfully prepared, which fully meets the performance requirements of "precision, accuracy, and delicacy" for high-density, miniaturized electronic packaging.

[0057] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and the scope of protection of the present application is defined by the appended claims, the specification and their equivalents.

Claims

1. A method for preparing a one-part, low flow, low cure shrinkage epoxy electronic adhesive, characterized in that, The epoxy electronic adhesive is prepared by ball milling and curing under temperature gradient, and the epoxy electronic adhesive is prepared from epoxy resin, high-flexibility reactive toughening agent, adhesion promoter, hydrophobic filler, latent curing agent and curing accelerator; wherein the latent curing agent is one or more of boron trifluoride-monoethylamine complex, modified imidazole, dicyandiamide, modified dicyandiamide, ketimine, aldimine, iodonium salt and sulfonium salt; the high-flexibility reactive toughening agent is one or more of carboxyl-terminated nitrile rubber, amino-terminated nitrile rubber, hydroxyl-terminated nitrile rubber, polyethylene glycol, hydroxyl-containing polyester and hydroxyl-containing polyacrylate; and the hydrophobic filler is one or more of hydrophobic nano calcium carbonate, hydrophobic fumed silica, hydrophobic carbon black and hydrophobic titanium dioxide.

2. The production method according to claim 1, characterized by, The method comprises the following steps: S1, mixing the epoxy resin, high-flexibility reactive toughening agent and adhesion promoter according to a mass ratio of 1:(0.05-0.3):(0.01-0.05), ball milling at 100-200 rpm for 2-4 h to form a mixed resin A; S2, adding the hydrophobic filler to the mixed resin A according to a mass ratio of epoxy resin 1:hydrophobic filler (0.5-5), and ball milling at 100-200 rpm for 4-8 h to form a mixed resin B; S3, adding the latent curing agent and curing accelerator to the mixed resin B according to a mass ratio of epoxy resin 1:latent curing agent (0.1-0.3):curing accelerator (0.01-0.1), and ball milling at 100-200 rpm for 1-2 h to obtain the epoxy electronic adhesive.

3. The production method according to claim 1, characterized by, The latent curing agent is one or more of modified imidazole and modified dicyandiamide.

4. The method of claim 1, wherein, The high-flexibility reactive toughening agent is hydroxyl-terminated nitrile rubber.

5. The preparation method according to claim 4, characterized in that, The number average molecular weight of the hydroxyl-terminated nitrile rubber is 1500-4000 g / mol.

6. The method of claim 1, wherein, The hydrophobic filler is one or more of hydrophobic fumed silica and hydrophobic carbon black.

7. The preparation method according to claim 1, characterized in that, The epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin and hydrogenated bisphenol A type epoxy resin.

8. The method of claim 1, wherein, The adhesion promoter is one or more of amino silane coupling agent, epoxy silane coupling agent, methacryloxy silane coupling agent and titanate coupling agent.

9. The method of claim 1, wherein, The curing accelerator is one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 4-chlorophenyl-N,N-dimethylurea, benzyldimethylamine, triethanolamine, tris(dimethylaminomethyl)phenol, benzyltriethylammonium chloride and tetrabutylammonium bromide.