Conductive adhesive, application of conductive adhesive and electronic device

Abstract

The invention discloses a conductive adhesive, application of the conductive adhesive and an electronic device. The conductive adhesive comprises the following components in percentage by mass: 5-30% of a conductive organic compound; 15%-30% of curable resin; and 30%-70% of a solvent. The conductive adhesive has the advantages that the process flexibility is high, an electroplating seed layer in the electroplating process can be replaced by the conductive adhesive, the binding force is good, more convenience is provided for the subsequent electroplating process, the diffusion of electroplating liquid can be avoided, and the conductive adhesive can be realized through the technological processes of coating, curing and the like in application, so that the production efficiency can be improved.

Description

Technical Field

[0001] This application relates to materials used in the manufacture of devices, and more particularly to a conductive adhesive, the application of the conductive adhesive, and electronic devices. Background Technology

[0002] In wafer-level packaging and printed circuit board manufacturing, electroplating is often used to construct metal interconnect structures. A prerequisite for electroplating is the preparation of a continuous, dense, and conductive seed layer on an insulating substrate. Currently, seed layers are primarily achieved using physical vapor deposition (PVD) techniques such as sputtering to prepare thin films of metals (e.g., copper, titanium). This traditional process is limited by high equipment costs, high and uneconomical process costs, and substrate limitations. For example, sputtering equipment and related facilities require substantial investment and maintenance costs; the process requires maintaining a high-vacuum environment with low target utilization; and high-temperature and plasma environments are unfavorable for heat-sensitive substrates. With the development of existing technologies, the demand for electroplating on heat-sensitive substrates such as flexible polymers is increasing. For further development, the semiconductor industry, with its heavy equipment and instrumentation assets, urgently needs a method and materials with good electroplating compatibility that can be implemented through low-cost and simple processes to replace traditional PVD metal seed layers. Summary of the Invention

[0003] This application discloses a conductive adhesive and its application and a metal interconnect structure. The conductive adhesive can replace the electroplating seed layer in the electroplating process and can improve production efficiency.

[0004] To achieve the above objectives, in a first aspect, this application discloses a conductive adhesive. The conductive adhesive, by weight percentage, comprises: Conductive organic compounds: 5%-30%; Curable resin: 15%-30%; Solvent: 30%-70%.

[0005] In some embodiments, the conductive organic compound includes conductive polymers and their derivatives.

[0006] In some embodiments, the conductive polymer compound and its derivatives include at least one of PEDOT:PSS, polyaniline, polypyrrole and its derivatives.

[0007] In some embodiments, the curable resin includes at least one of a photocurable resin and a thermocurable resin; When the curable resin includes light-curable resin and thermo-curable resin, 0 < light-curable resin ≤ 27%; 30% ≥ thermo-curable resin ≥ 3%.

[0008] In some embodiments, when the curable resin includes the photocurable resin, the conductive adhesive includes a photoinitiator in the form of 1%-3%; and / or, the photocurable resin includes epoxy acrylate or polyurethane acrylate. When the curable resin includes the thermosetting resin, the conductive adhesive includes a thermosetting agent, the proportion of which is 0.5%-4%, and / or the thermosetting resin includes a modified epoxy resin, a phenolic resin, or a polyimide precursor.

[0009] In some embodiments, the conductive adhesive includes a conductivity enhancer, wherein the conductivity enhancer accounts for 2%-5%.

[0010] In some embodiments, the conductivity enhancer includes polyols and sugar alcohols, polar aprotic solvents, or ionic liquids.

[0011] In some embodiments, the conductive adhesive includes an adhesion promoter at a concentration of 0.3%-1%.

[0012] In some embodiments, the adhesion promoter includes silanes, organotitanium / aluminum compounds, or polymeric surfactants.

[0013] Secondly, this application discloses the application of conductive adhesive. The conductive adhesive is any of the aforementioned conductive adhesives, and it is used for the connection between components of electronic devices.

[0014] In some embodiments, the conductive adhesive is applied in a semiconductor process, which includes the following steps: The conductive adhesive is cured; The cured conductive adhesive is then subjected to subsequent processes.

[0015] In some embodiments, the subsequent processes include photolithography and electroplating.

[0016] Thirdly, this application discloses an electronic device. The electronic device includes a conductive structure and elements connected through the conductive structure, wherein the conductive structure includes any of the aforementioned conductive adhesives and the conductive adhesive is cured.

[0017] In some embodiments, the electronic device includes a metal interconnect structure, which includes the conductive structure.

[0018] Regarding the aforementioned conductive adhesives, their applications, and electronic devices, since the conductive adhesives include conductive organic compounds, curable resins, and solvents, etc., and each falls within the aforementioned scope, the conductive adhesives have at least the following advantages: 1) High process flexibility: For example, the composition of the curable resin can be adjusted according to the needs, and it can adapt to different equipment or product requirements. For example, the curable resin can be a light-curing resin, a thermosetting resin, or a light-thermal dual-curing resin that can be cured by light and heat.

[0019] 2) The conductive adhesive described can replace the electroplating seed layer in the electroplating process. It is low-cost and simple to process; for example, it eliminates the need for physical vapor deposition (PVD) methods such as sputtering to prepare the metal seed layer, and reduces reliance on PVD equipment by eliminating the need for PVD processes. Therefore, costs are significantly reduced, the process is simpler, which is more conducive to the further expansion of production in the related semiconductor industry, and also significantly reduces energy consumption.

[0020] 3) Based on the strength of the conductive organic compound, curable resin and solvent, the conductive adhesive has good bonding force. The bonding force includes cohesion (the strength of the conductive adhesive itself) and adhesion (the bonding strength between the conductive adhesive and other materials). Therefore, when the conductive adhesive is combined with photoresist or substrate, the bonding force between the conductive adhesive of this application and them is better than the bonding force between the metal seed layer and them. The better bonding force provides more convenience for the subsequent electroplating process and helps to avoid the diffusion of electroplating solution.

[0021] 4) High production efficiency: The conductive adhesive can be formed by spin coating, etc., without PVD process. PVD process requires equipment start-up time and other time, while spin coating and other processes have shorter equipment start-up time than PVD. Therefore, the conductive adhesive can reduce process production time, shorten the construction period of multi-layer processes, and improve equipment reuse rate when applied.

[0022] Fourthly, this application discloses a conductive adhesive, wherein the conductive adhesive comprises, by weight percentage: Conductive organic compounds: 5%-30%; Thermosetting resin: ≤2%; UV-curable resin: 50%-60%; Diluent: 35%-55% In some embodiments, the conductive organic compound includes conductive polymers and their derivatives.

[0023] In some embodiments, the conductive polymer compound and its derivatives include at least one of PEDOT:PSS, polyaniline, polypyrrole and its derivatives.

[0024] In some embodiments, the conductive adhesive includes a conductivity enhancer, wherein the conductivity enhancer accounts for 2%-7%.

[0025] In some embodiments, the conductivity enhancer includes polyols and sugar alcohols, polar aprotic solvents, or ionic liquids.

[0026] Fifthly, this application discloses an electronic device, the electronic device including a conductive structure, the conductive structure being formed by 3D printing from at least any of the aforementioned conductive adhesives.

[0027] The conductive adhesive described above has the following advantages in 3D printing: 1) High printing speed and molding efficiency. For example, the photocurable resin, as a continuous phase, is the skeleton for achieving precise 3D molding. The above-mentioned amount of photocurable resin allows each layer of material to be completely cured in a very short time (seconds) under ultraviolet light irradiation, thus resulting in high printing speed and molding efficiency. 2) High printing resolution and shape fidelity. For example, the diluent content mentioned above helps the resin slurry have extremely low viscosity, enabling rapid leveling and the formation of a uniform thin layer. The UV-cured resin can "freeze" the pattern in each layer, preventing material flow and pattern distortion caused by slow curing. 3) Good interlayer bonding and low internal stress, for example: the shrinkage during the photocuring process is relatively controllable, and each layer is fully cured. A small amount of thermosetting resin (≤2%) can ensure good overall structural integrity and prevent cracking or warping due to internal stress; 4) Employing a dual curing mechanism of "photocuring + thermal curing," photocuring cannot be completed for areas that cannot be reached by light (such as the bottom of components or shadow areas of complex three-dimensional structures). In these cases, less than or equal to 2% of the thermally curing resin reacts during subsequent heating, ensuring complete curing in these areas and achieving curing without dead corners, significantly improving reliability. Ultimately, the two thermal curing processes facilitate further cross-linking, enhancing the overall thermal stability, mechanical strength, and long-term durability of the printed device. Detailed Implementation

[0028] To illustrate the technical content, structural features, achieved objectives, and effects of the invention in detail, the technical solutions in the embodiments of this application will be described below. Obviously, the described embodiments are merely a part of the embodiments of this application, and not all of them. In the following description, for illustrative purposes, numerous specific details are set forth to provide a detailed description of various exemplary embodiments or implementations of the invention. However, various exemplary embodiments may also be implemented without these specific details or in one or more equivalent arrangements. Furthermore, the various exemplary embodiments may differ, but are not necessarily exclusive. For example, the specific shape, construction, and characteristics of the exemplary embodiments may be used or implemented in another exemplary embodiment without departing from the inventive concept.

[0029] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0031] In this application, unless otherwise expressly specified and limited, the term "connection" shall be interpreted broadly. For example, "connection" may be a fixed connection, a detachable connection, or an integral part; it may be a direct connection or an indirect connection through an intermediate medium.

[0032] This application discloses a conductive adhesive. It comprises a conductive organic compound, a curable resin, and a solvent. The components are described below by weight percentage: Conductive organic compound: 5%-30%; for example, 5%, 7%, 9%, 10%, 12%, 13%, 15%, 17%, 19%, 20%, 22%, 23%, 25%, 26%, 27%, 28%, 29%, or 30%. One function of the conductive organic compound is to provide conductive pathways. The content of the conductive organic compound within the above range can give the conductive adhesive good conductivity, flowability (facilitating coating or printing), adhesive strength, and mechanical strength, which is beneficial for enhancing cohesion and reducing costs. Cohesion is one aspect of bonding strength; therefore, strong cohesion can also be understood as resulting in good bonding strength of the conductive adhesive. More specifically, if the content is less than 5%, the following disadvantages exist: 1.1) Conductive ions cannot form effective contact in the resin matrix, and cannot form an effective three-dimensional conductive network. As a result, the conductivity is low, or the dispersion uniformity of trace conductive organic compounds is difficult to control, leading to large fluctuations in conductivity; 1.2) The bonding force is weak. The bonding force includes cohesion and adhesion. Specifically, because the content is less than 5%, it is easy to cause uneven distribution of conductive organic compounds in the interface area, which in turn leads to weak adhesion. If it is enriched at the interface, it will hinder the close contact between the resin and the substrate, forming a weak interface layer; if the interface is missing: although the resin is in direct contact with the substrate, the material properties of the interface area are inconsistent with the bulk. Under environmental stress, failure may occur near the interface due to modulus mismatch. Therefore, uneven mixing in the interface area will result in poor or weak adhesion. If the content exceeds 30%, at least one of the following disadvantages exists: 1) Deterioration in processability: Excessive solid content leads to excessive viscosity and poor flowability of the colloid, making it difficult to perform fine processing such as screen printing, precision dispensing, or spraying; 2) Deterioration in mechanical properties: Excessive conductive organic compounds can disrupt the continuous phase of the resin, resulting in increased brittleness, decreased cohesion, and easy cracking or detachment from the substrate after curing; Furthermore, during coating and curing, excessive conductive organic compounds may accumulate at the interface, forming a weak interface layer dominated by conductive organic compounds, which will hinder the bonding of the conductive adhesive with other materials, leading to decreased adhesion. Conductive organic compounds within the above-mentioned range can avoid the above problems; 3) Increased cost: Conductive organic compounds (such as high-performance PEDOT:PSS) are usually expensive, and excessive use is uneconomical.

[0033] Curable resin: 15%-30%, for example, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%. The curable resin provides structural strength and adhesive properties, etc. Within the above range, the curable resin acts like a network or skeleton, encapsulating and fixing all other components, including the conductive organic compound, bonding them into a whole to form a continuous structural phase. This provides good mechanical support and protection, ensuring both mechanical and electrical long-term stability. Furthermore, while providing excellent mechanical properties and adhesive reliability, the curable resin content leaves sufficient space for the conductive organic compound and solvent, ensuring suitable fluidity of the system before curing and a sufficiently high proportion of conductive pathways after curing. More specifically, if the content is less than 15%, at least one of the following disadvantages exists: 1) Poor mechanical strength: With a low content, the resin is insufficient to form a complete and tough three-dimensional cross-linked network, which cannot effectively encapsulate other materials. After curing, the adhesive layer has low cohesion and is brittle, making it prone to cohesive failure under external force; 2) If the content is less than 15%, there is not enough resin, resulting in insufficient adhesive material reaching the interface and weak adhesion; 3) Adhesion failure: Insufficient adhesive force is provided, resulting in insufficient adhesion between the adhesive layer and the substrate, making it easy for the interface to peel off; 4) Insufficient coating and protection: The coating and fixing effect on conductive organic compounds is weakened, which may cause conductive organic compounds to easily fall off or migrate, affecting long-term reliability. If the content is greater than 30%, at least one of the following disadvantages exists: 1) Limited conductivity: The higher content relatively squeezes the effective volume ratio of conductive organic compounds, which may lead to a decrease in the density of conductive pathways and a decrease in conductivity; 2) High curing shrinkage stress: If the resin content is too high, the shrinkage stress generated during curing will increase, which may lead to chip warping, substrate deformation or microcracks at the interface and increased brittleness, resulting in poor cohesion; 3) If the content is too high, the excessive shrinkage stress will cause the adhesive layer to lift off the edge of the substrate, causing interface damage; 4) Cost and processability: Some high-performance resins are expensive, and excessive use is uneconomical, which may also lead to a higher initial viscosity of the system.

[0034] Solvent: 30%-70%, for example, 30%, 32%, 34%, 35%, 37%, 38%, 40%, 41%, 43%, 45%, 48%, 50%, 52%, 55%, 57%, 58%, 60%, 62%, 64%, 65%, 67%, 68%, 69%, or 70%. The solvent can adjust processing properties, such as viscosity. Within the above range, the solvent ensures that the conductive organic compound and curable resin are uniformly dispersed, forming a stable and homogeneous slurry. Furthermore, while ensuring processability, it avoids a series of problems caused by excessive solvent, ensuring that the adhesive film has sufficient thickness and solids content before curing to meet the size and strength requirements of the joints. If the solvent content is less than 30%, at least one of the following disadvantages exists: 1) Poor processability: The system is too viscous, with poor flowability, making it impossible to perform screen printing, inkjet printing, or uniform coating. Problems such as tailing, stringing, and uneven dispensing are easily generated. 2) Difficulty in dispersion: It is difficult to uniformly disperse conductive organic compounds and curable resins, which easily leads to agglomeration and uneven conductivity. If the content is greater than 70%, at least one of the following disadvantages exists: 1) Many defects after curing: After excessive solvent evaporation, too many pores or shrinkage cavities will be left in the adhesive layer, which will seriously reduce the density, mechanical strength and conductivity reliability of the adhesive layer (for example, the circuit may be broken); 2) The adhesive layer is too thin / insufficient in strength: If the solid content is too low, the adhesive film formed after curing is too thin and cannot meet the required bonding thickness, mechanical strength or insulation / thermal conductivity requirements.

[0035] As described above, since the conductive adhesive comprises conductive organic compounds, curable resins, and solvents, each within the aforementioned range, their interaction offers at least the following advantages: 1) High process flexibility: For example, the composition of the curable resin can be adjusted according to requirements to adapt to different equipment or product requirements. For example, the curable resin can be a photocurable resin, a thermocurable resin, or a photothermal dual-curable resin that can be cured by light and heat. The photothermal dual-curable resin includes: 1) two types of resin, one is a photothermal resin and the other is a thermocurable resin; 2) one type of resin that can be cured by both light and heat.

[0036] 2) The conductive adhesive can replace the electroplating seed layer in the electroplating process, thus reducing costs and simplifying the process. For example, it eliminates the need to prepare a metal seed layer through physical vapor deposition methods such as sputtering, and reduces reliance on PVD equipment by eliminating the need for PVD processes. Therefore, costs are significantly reduced, the process is simpler, which is more conducive to the further expansion of production in the related semiconductor industry, and also significantly reduces energy consumption.

[0037] The following is a table showing some relevant properties of the conductive adhesive and the metal seed layer of this application: nature conductive adhesive PVD thin film seed layer resistivity <![CDATA[10 -3 Oh—10 -5 Oh]]> <![CDATA[10 -6 Oh—10 -7 Oh]]> Photoresist adhesion Second only to similar photoresists of the same layer <![CDATA[10 -1 Mpa—10 -2 Mpa]]> thermal stability Stable below 150℃ Applicable to most scenarios Metal bonding properties <![CDATA[10 -1 Mpa—10 -2 Mpa]]> Intermetallic bonding Scope of application Low cost, simple process, suitable for mass market applications It is costly and has a complex manufacturing process, making it suitable for high-precision fields with high conductivity requirements. 3) Based on the foregoing explanation of the strength of the conductive organic compound, curable resin and solvent, the conductive adhesive has good bonding strength, which includes cohesive strength (the strength of the conductive adhesive itself) and adhesion strength (the bonding strength between the conductive adhesive and other materials). Therefore, when the conductive adhesive is combined with photoresist or substrate, the bonding strength between the conductive adhesive of this application and them is better than the bonding strength between the metal seed layer and them. Better bonding strength provides more convenience for subsequent electroplating processes, helps to avoid process problems such as electroplating solution diffusion, photoresist detachment, and structural deformation, and can also prevent seed layer peeling and reduce transportation costs.

[0038] 4) High production efficiency: The conductive adhesive can be formed by spin coating, etc., without PVD process. PVD process requires time to accumulate thickness, etc., which takes a long time. Spin coating and other processes have shorter equipment start-up time than PVD. Therefore, the conductive adhesive can reduce process production time, shorten the construction period of multi-layer processes, and improve equipment reuse rate.

[0039] In some embodiments, the conductive organic compound includes a conductive polymer and its derivatives. The conductive polymer and its derivatives include at least one selected from PEDOT:PSS, polyaniline, polypyrrole, and its derivatives.

[0040] As described above, using conductive polymer compounds and their derivatives has at least one of the following advantages: 1) Improve flexibility and conductivity. The conductive network formed by conductive polymer compounds and their derivatives has intrinsic flexibility, which enables the cured conductive adhesive layer to maintain excellent conductivity. At the same time, the cured conductive adhesive has good flexibility, good bending and tensile properties, and the conductive path is not easily broken under repeated bending or dynamic loads, and the resistance change is small.

[0041] 2) Improved reliability: Conductive polymer compounds and their derivatives can form effective conductivity without high-temperature sintering, enabling the conductive adhesive to work synergistically with the curable resin system to achieve rapid curing and high-strength connection at low temperatures, and fundamentally avoid circuit failure caused by metal migration, thus significantly improving connection reliability.

[0042] 3) Improved process and cost advantages: Conductive polymer compounds and their derivatives usually exist in solution form, have good compatibility with resin matrix, are easy to process and have stable formulations.

[0043] In some embodiments, when the curable resin includes a photocurable resin and a thermocurable resin, 0 < photocurable resin ≤ 27%; 30% > thermocurable resin ≥ 3%.

[0044] As described above, the ratio within this range offers the following advantages: within this range, the photocurable resin can rapidly solidify the structure, reducing waiting time during production and making it suitable for large-scale continuous production. Simultaneously, photocuring ensures rapid surface formation, prevents dripping, and reduces the possibility of contamination during the process. Subsequent thermocuring guarantees overall density, strong adhesion, and final electrical properties.

[0045] When the curable resin includes the photocurable resin, the conductive adhesive includes a photoinitiator, and the proportion of the photoinitiator is 1%-3%, for example, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%.

[0046] As described above, the photoinitiator content within the aforementioned range offers at least one of the following advantages: 1) It ensures a sufficient, rapid, and controllable photocuring reaction with stable electrical properties. This is because the specified content ensures the generation of a sufficient number of free radicals under UV irradiation, achieving surface drying or "setting" of the colloid within seconds to tens of seconds, completing initial fixation, and meeting production cycle requirements. The aforementioned content is sufficient to handle certain formulation fluctuations, ensuring curing depth and completeness. Thus, while ensuring rapid curing, it avoids the negative impacts of excessive initiator. 2) It optimizes the overall performance of the final material: 2.1) It avoids "over-crosslinking" and embrittlement: Excessive photoinitiator generates too many free radicals, leading to excessively high local crosslinking density, increasing the brittleness and reducing the flexibility of the cured adhesive layer, making it prone to microcracks; 2.2) It prevents yellowing and aging: Controlling the content below 3% can significantly reduce or delay the yellowing phenomenon of the adhesive layer, improving the product's appearance stability and long-term durability.

[0047] In some embodiments, the photocurable resin comprises epoxy acrylate or polyurethane acrylate. This configuration has the following advantages: 1) Epoxy acrylate provides a robust "skeleton" for the network composed of conductive organic compounds: its high modulus and high strength network effectively supports and fixes the flexible conductive polymer network, preventing it from undergoing plastic deformation under stress that would lead to drastic changes in resistance. This ensures the conductivity of the conductive adhesive while improving the mechanical stability of the conductive pathway. When the conductive adhesive includes an adhesion promoter, epoxy acrylate exhibits good solvent compatibility, is easily formulated to a suitable viscosity for coating, and its high polarity also helps to form stronger interfacial interactions with polar conductive polymers and adhesion promoters (such as silane coupling agents). Ultimately, the molecular weight, functionality, and crosslinking density of epoxy acrylate contribute to good cohesion in the conductive adhesive, resulting in good bonding strength.

[0048] 2) The flexibility of polyurethane acrylate itself can match the flexibility of conductive polymers of conductive organic compounds to form an integrally flexible composite film. This can avoid stress concentration and breakage of the conductive layer at bending points due to excessive hardness of the resin matrix, and also contributes to the good adhesion of the conductive adhesive.

[0049] 3) If photothermal curing is used in the conductive adhesive application, the extremely high photocuring activity of the resin ensures that the colloid can achieve precise shaping within tens of seconds, providing an ideal pretreatment state for subsequent thermal curing. The combination of both with the thermosetting resin optimizes the efficiency of the photothermal dual-curing process.

[0050] In some embodiments, when the curable resin includes the thermosetting resin, the conductive adhesive includes a thermosetting agent, and the proportion of the thermosetting agent is 0.5%-4%. For example, 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.7%, 1.9%, 2%, 2.2%, 2.3%, 2.5%, 2.7%, 3%, 3.2%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4%.

[0051] As described above, the thermosetting agent within the above-mentioned range has at least one of the following advantages: 1) Ensure a full and thorough thermosetting reaction: The above-mentioned content ensures that, under heating conditions, sufficient thermosetting agent molecules react with the active groups (such as epoxy groups) of the thermosetting resin to form a highly cross-linked three-dimensional network, thereby achieving the final high strength (strength is beneficial for good cohesion, and consequently, good bonding), high heat resistance, and high chemical stability. The above-mentioned content can compensate for losses caused by process fluctuations (such as uneven mixing and trace moisture loss), ensuring that full curing can be achieved even under less than ideal conditions.

[0052] 2) Optimizing the overall performance and reliability of the final material: 2.1) Avoiding "over-crosslinking" and embrittlement: Excessive thermosetting agent may lead to excessively high crosslinking density, causing the polymer network to become brittle, reduce toughness, and increase internal stress, thereby reducing the impact resistance and fatigue resistance of the adhesive layer and making it prone to cracking during thermal cycling. 2.2) Reducing small molecule residues and migration: Unreacted thermosetting agents (such as certain amine curing agents) or their byproducts may remain in the adhesive layer, becoming migratable small molecules. These substances may slowly precipitate, leading to increased contact resistance, corrosion of adjacent metal circuits, or contamination of sensitive devices. The above-mentioned content can avoid such residues and reduce migratable small molecules.

[0053] In some embodiments, the thermosetting resin includes a modified epoxy resin, a phenolic resin, or a polyimide precursor. This configuration offers the following advantages: 1) Modified epoxy resin: 1.1) The chemical structure of modified epoxy resin is highly similar to that of commonly used epoxy acrylate photocurable resins, or they can be linked by chemical bonds to form a uniform, interpenetrating, or covalently bonded rigid-rigid reinforced network with high interfacial strength. 1.2) The high modulus and high strength cured network of modified epoxy resin acts like a robust "mold" or "skeleton," fixing the network of soft conductive organic compounds within it, preventing irreversible plastic deformation and resistance drift under mechanical or thermal stress. This provides superior mechanical stability of the conductive pathway, ensuring long-term stability of electrical signals under vibration and impact. 1.3) When the conductive adhesive includes an adhesion promoter, the abundant polar groups of modified epoxy resin react strongly with silane coupling agents, greatly enhancing adhesion to various substrates.

[0054] 2) Phenolic resin: When phenolic resin is combined with a UV-curing agent, it forms a composite structure of a "tough preliminary skeleton" + a "rigid fire-resistant fortress," improving its high-temperature resistance and flame retardancy. When phenolic resin is combined with conductive organic compounds, ordinary resins soften and fail at high temperatures, but phenolic resin remains rigid. It provides "anchor points" for the network composed of conductive organic compounds at high temperatures, preventing the conductive network from loosening or being destroyed due to matrix softening at high temperatures, thus achieving high-temperature reliability of the conductive function.

[0055] 3) Polyimide precursor: The resulting polyimide has high thermal and dimensional stability, providing a near-inert and robust "protective shell" for conductive organic compounds, enabling them to function normally in extreme temperatures and harsh chemical environments.

[0056] In some embodiments, the conductive adhesive includes a conductivity enhancer, the proportion of which is 2%-7%, for example, 2%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 5.2%, 5.5%, 5.7%, 5.9%, 6%, 6.2%, 6.5%, 6.6%, 6.8%, or 7%.

[0057] As described above, the conductivity enhancer, within the aforementioned range, can effectively improve conductivity. This is because if the concentration is below 2%, phase separation and chain rearrangement are insufficient, resulting in minimal conductivity improvement. If the concentration is above 7%, it may damage the network or cause over-plasticization: excessive small molecules may cause PEDOT to swell excessively or interfere with resin curing, reducing the hardness, modulus, and cohesiveness of the conductive adhesive, ultimately leading to decreased conductivity and deteriorated mechanical properties. Therefore, a conductivity enhancer concentration of 2%-7% maximizes conductivity. Furthermore, within the aforementioned range, the conductivity enhancer indirectly contributes to improved bonding strength. Specifically, thanks to the significant increase in conductivity efficiency from the conductivity enhancer, fewer "conductive organic compounds" achieve the same conductivity target, thus leaving more space for the curable resin to build a strong network, ultimately indirectly improving bonding strength (especially cohesiveness).

[0058] In some embodiments, the conductivity enhancer includes polyols and sugar alcohols (e.g., sorbitol, ethylene glycol, polyethylene glycol), polar aprotic solvents (e.g., DMSO, DMF), and ionic liquids (e.g., third-generation ionic liquids).

[0059] As described above, when the conductivity enhancer includes polyols and sugar alcohols, it has the following advantages: 1) Polyols / sugar alcohols contain multiple hydroxyl groups (-OH), which can interact with conductive organic compound molecules (such as PEDOT:PSS, polyaniline, etc.) through hydrogen bonds, improving their dispersibility in the resin system, preventing aggregation, and thus forming a more uniform and continuous conductive network; 2) For some conductive polymers, polyols can weaken the tight packing between their molecular chains, enhance chain segment movement, facilitate carrier migration, and improve conductivity; 3) It is beneficial for the above-mentioned conductive adhesive to replace the metal seed layer because: 3.1) Polyols can significantly reduce the surface tension of the conductive adhesive, allowing it to better wet and spread on hydrophobic or low surface energy substrates (such as many engineering plastics), forming a more uniform and continuous film, reducing pinholes, and thus providing excellent wetting and spreading, facilitating electroplating; 3.2) Hydroxyl groups can form hydrogen bonds with polar groups on the substrate surface, improving initial adhesion. Simultaneously, as a plasticizer, it can alleviate curing stress and reduce delamination caused by shrinkage, thereby enhancing adhesion.

[0060] When the conductivity enhancer includes a polar aprotic solvent, the polar aprotic solvent can partially dissolve or swell the conductive polymer, significantly improving carrier mobility. In some cases, the polar aprotic solvent can make the bulk resistivity of the conductive organic compound (PEDOT:PSS) approach or reach the level of a metal seed layer, thus replacing the metal seed layer. For materials like PEDOT:PSS, the polar aprotic solvent can partially remove the insulating phase of PSS, promoting the formation of a more effective percolation network in the conductive regions of PEDOT. Furthermore, the polar aprotic solvent promotes the densification of the conductive network: by adjusting the molecular chain conformation, the conductive polymer forms a denser, less defective conductive network, increasing coating density, blocking electroplating solution penetration, and achieving better electroplating results.

[0061] When the conductivity enhancer includes an ionic liquid, the ionic liquid itself can not only improve electronic conductivity (through "secondary doping" of the conductive polymer), but also provide ionic conductivity, ensuring that even when there are minor defects in the conductive polymer network, the overall conductivity can still be maintained through ion migration, reducing the risk of uneven current in the initial stage of electroplating; the ionic liquid can also act as a surfactant to improve the dispersion of conductive organic compounds and the wetting of the substrate, forming a dense and smooth film, which is beneficial for subsequent electroplating of a uniform and bright metal layer.

[0062] In some embodiments, the conductive adhesive includes an adhesion promoter at a concentration of 0.3%-1%, for example, 0.3%, 0.32%, 0.35%, 0.37%, 0.4%, 0.42%, 0.43%, 0.45%, 0.47%, 0.5%, 0.52%, 0.55%, 0.58%, 0.6%, 0.62%, 0.65%, 0.67%, 0.7%, 0.72%, 0.75%, 0.77%, 0.8%, 0.82%, 0.85%, 0.87%, 0.9%, 0.93%, 0.95%, 0.97%, or 1%.

[0063] As described above, within the specified range, the adhesion promoter can form a uniform and dense chemically bonded layer on the substrate surface, resulting in good and stable adhesion. If the concentration is below 0.3%, the minimum effective concentration required to form a nearly complete monomolecular chemical adsorption layer on the substrate surface cannot be achieved; instead, sparse and discontinuous "patch"-like bonding points will form, leading to poor adhesion. If the concentration is above 1%, excess molecules will not find anchoring points at the interface. Excess adhesion promoter cannot fully react with the substrate, forming physically stacked multi-molecular layers at the interface. These unreacted molecular layers have low cohesive strength, creating a fragile "weak boundary layer," resulting in a decrease in adhesion instead of an increase.

[0064] In some embodiments, the adhesion promoter includes silanes (such as HMDS, other silane coupling agents), organotitanium / aluminum compounds (such as phthalate coupling agents), and polymeric surfactants (such as SurPass).

[0065] As described above, it has the following advantages: 1) When silanes are used, they provide chemical bonding, establishing the strongest covalent bond connection at the inorganic / organic interface, which greatly improves wet adhesion and hydrolysis resistance, and is beneficial to the electroplating process.

[0066] 2) When organic titanium / aluminum is used, the alkoxy groups of titanate / aluminate can react with protons or trace amounts of water on the substrate surface. The central metal atom (Ti or Al) has a strong coordination ability and can form coordination bonds with various atoms (such as P, S, O) on the substrate surface. It can be strongly adsorbed even on surfaces without hydroxyl groups, thereby improving the bonding strength and corrosion resistance of the interface, and making the adhesion stronger.

[0067] 3) When a polymeric surfactant is used, it can adjust the spatial distribution of polymeric branches and the surface tension of conductive adhesive, which can prevent large-area bulging or cracking of the plating layer due to stress after electroplating.

[0068] Secondly, this application discloses the application of any of the aforementioned conductive adhesives, which are used for connections between electronic devices, replacing soldering, chip packaging, printed circuit boards, and other fields. In addition, the proportion of photothermal curing agent in the conductive adhesive can be adjusted, and photosensitive resins or low-melting-point thermoplastics can be selected, allowing it to replace the traditional pattern transfer process of photolithography and electroplating. The desired circuit pattern can be formed only after photolithography development. For example, this application is more suitable for general applications such as printed circuit boards. Examples of some applications of the conductive adhesive are as follows: 1) Applications in advanced semiconductor packaging and assembly: 1.1) Chip bonding: used to bond low-heat-generating chips such as power chips, LED chips, and RF chips to the packaging substrate or lead frame; 1.2) Flip chip underfill: fills the gap between the chip and the substrate, providing mechanical support and stress buffer; 1.3) 3D packaging and through-silicon via interconnect: used for temporary vertical interconnects between stacked chips or temporary conductive fixation of TSVs.

[0069] 2) Applications in 3D printing: The conductive adhesive can be used in processes such as direct writing and inkjet printing to directly manufacture high-resolution three-dimensional circuits, flexible sensors, and three-dimensional interconnect structures, such as three-dimensional circuits, spring-shaped interconnects, antennas, micro-circuits, sensor electrodes, and mechanical load-bearing structures. It is also a component with circuit functions (such as drone wings with sensing functions and smart furniture shells).

[0070] 3) Applications in printed electronics and flexible electronics manufacturing, such as in printed circuit boards, where the conductive adhesive is used for the manufacture of antennas, sensors, and circuits; in flexible displays, where the conductive adhesive is used for the interconnection and repair of flexible electrodes in OLED and Micro-LED display panels; and in wearable devices, where the conductive adhesive is used to achieve flexible and stretchable electrical connections in smart fabrics, electronic skin, and wristband devices.

[0071] 4) Applications of photovoltaics and new energy: For example, in crystalline silicon solar cells, the conductive adhesive replaces the traditional lead-containing solder ribbon for lead-free, low-temperature interconnection between cells; and in thin-film / flexible solar cells, the conductive adhesive is used to make transparent electrodes and internal connections, suitable for building-integrated photovoltaics and portable charging devices.

[0072] In some embodiments, the conductive adhesive is applied in a semiconductor process, which includes the following steps: curing the conductive adhesive; and performing subsequent processes on the cured conductive adhesive. The subsequent processes include photolithography and electroplating. For example, the semiconductor process includes a metal interconnect process, which includes: coating the conductive adhesive → pre-drying → curing (e.g., photocuring → thermal curing) → photolithography (coating, pre-baking, photolithography, post-baking, development, hard baking) → electroplating. Traditional metal interconnect processes include: PVD composite seed layer → photolithography (coating, pre-baking, photolithography, post-baking, development, hard baking) → electroplating. Comparing the two processes, it can be seen that the conductive adhesive of this application can replace the PVD composite seed layer; for example, applicable electroplating metals include nickel, titanium, and chromium.

[0073] The following describes the steps involved in applying the conductive adhesive: Implementation Method 1 (Photothermal Curing): Coating: The conductive adhesive is applied to the substrate by spin coating, scraping, or other methods to form a uniform and smooth wet film.

[0074] Pre-baking: Heat at 60-100℃ for 1-5 minutes to remove most of the solvent.

[0075] Photocuring: Ultraviolet light (300-400nm, 300-2000mJ / cm2) is used to rapidly form the adhesive layer surface.

[0076] Thermosetting: Heat at 100-250℃ for 10-120 minutes to allow the resin to fully cross-link.

[0077] Implementation Method Two (Photothermal Curing) Formulation: Polypyrrole dispersion (15%), epoxy acrylate (20%), modified epoxy resin (15%), 1-hydroxycyclohexylphenyl ketone (3%), DMSO (3%), KH-560 silane coupling agent (1%), N-methylpyrrolidone (43%) Process flow: 1. Spin-coat the conductive adhesive onto the wafer. 2. Pre-bake at 90°C for 5 min. 3. Expose to UV light at 1000 mJ / cm² and cure at 95°C for 30 min.

[0078] Implementation Method 3 (Including only thermosetting) Formula adjustment: Remove UV-curable resin and photoinitiator components, and increase the proportion of thermosetting resin. Process adjustments: Remove UV exposure and extend thermosetting time. Results: Applicable to photosensitive or more complex substrates, the resulting adhesive layer is more stable, but the processing time is relatively longer.

[0079] Implementation Method 4 (Including only photocuring) Formula adjustment: Reduce the proportion of thermosetting resin and use a photocurable resin with richer functional groups to achieve rapid setting during UV exposure.

[0080] Process adjustment: Remove heat curing after exposure or shorten the time to achieve rapid molding of the adhesive layer.

[0081] Result: It can quickly set the adhesive layer and is suitable for products that require a transparent adhesive layer and have flexibility requirements.

[0082] Thirdly, this application discloses an electronic device. The electronic device includes a conductive structure, which comprises any of the aforementioned conductive adhesives, and the conductive adhesive is cured. The beneficial effects of the electronic device are similar to those of the aforementioned conductive adhesives, such as the beneficial effect of good adhesion, and will not be repeated here.

[0083] In some other embodiments, the electronic device includes a metal interconnect structure, which includes the conductive structure. The beneficial effects of the conductive adhesive in the metal interconnect structure are similar to those described above regarding the beneficial effects of the conductive adhesive, such as its good adhesion, and will not be repeated here.

[0084] Furthermore, this application also discloses a second conductive adhesive. The conductive adhesive, by weight percentage, comprises: Conductive organic compounds: 5%-30%; Thermosetting resin: ≤2%; UV-curable resin: 50%-60%; Diluent: 35%-55%.

[0085] The conductive adhesive with the above components has the following advantages: 1) High printing speed and molding efficiency. For example, the photocurable resin, as a continuous phase, is the skeleton for achieving precise 3D molding. The photocurable resin with the above content enables each layer of material to be completely cured in a very short time (seconds) under ultraviolet light irradiation, thus resulting in high printing speed and molding efficiency.

[0086] 2) High printing resolution and shape fidelity. For example, the diluent content mentioned above helps the resin slurry have extremely low viscosity, enabling rapid leveling and the formation of a uniform thin layer. The UV-cured resin can "freeze" the pattern in each layer, preventing material flow and pattern distortion caused by slow curing. 3) Good interlayer bonding and low internal stress, for example: the shrinkage during the photocuring process is relatively controllable, and each layer is fully cured. A small amount of thermosetting resin (≤2%) can ensure good overall structural integrity and prevent cracking or warping due to internal stress; 4) Employing a dual curing mechanism of "photocuring + thermal curing," photocuring cannot be completed for areas that cannot be reached by light (such as the bottom of components or shadow areas of complex three-dimensional structures). In these cases, less than or equal to 2% of the thermally curing resin reacts during subsequent heating, ensuring complete curing in these areas and achieving curing without dead corners, significantly improving reliability. Ultimately, the two thermal curing processes facilitate further cross-linking, enhancing the overall thermal stability, mechanical strength, and long-term durability of the printed device.

[0087] In some embodiments, the conductive organic compound includes conductive polymers and their derivatives.

[0088] As described above, conductive polymers and their derivatives are polymers or colloidal particles that can be dissolved or stably dispersed in specific solvents / resins. Being organic systems along with the photocurable resin and diluent, they possess excellent compatibility and thermodynamic stability, allowing for the formulation of uniform and stable resin slurries. Unlike metal fillers, they do not settle or agglomerate during printing, ensuring consistent conductivity between the first and last layers and eliminating the need for frequent stirring before printing. Furthermore, conductive polymers and their derivatives are often added as nanoscale dispersed phases (such as aqueous or organic dispersions of PEDOT:PSS) or molecular-level solutions. Compared to micron / nanoscale metal particles, they contribute significantly less to the increase in resin system viscosity, which is beneficial for forming ultrathin, uniform coatings, enabling the printing of sub-millimeter or even micron-level fine features.

[0089] In some embodiments, the conductive polymer compound and its derivatives include at least one of PEDOT:PSS, polyaniline, polypyrrole and its derivatives.

[0090] When PEDOT:PSS is selected, it forms a highly stable colloidal dispersion in aqueous or polar organic solvents, exhibiting almost no sedimentation during storage and printing, resulting in extremely high process reliability. When polyaniline is selected, its conductivity can be reversibly controlled through pH and redox states, enabling its use in 3D printing of smart packaging, chemical / biological sensors, antistatic coatings, and electromagnetic shielding components. When polypyrrole is selected, it forms a strong interfacial bond with the photocurable resin matrix, resulting in flexible, bend-resistant printed parts that are less prone to delamination. Furthermore, a small amount of thermosetting resin (≤2%) further enhances the crosslinking of the polypyrrole network with the entire polymer matrix during the post-curing stage, improving overall integrity and durability.

[0091] In some embodiments, the conductive adhesive includes a conductivity enhancer, wherein the conductivity enhancer accounts for 2%-7%.

[0092] As described above, the conductivity enhancer within the above range has the following advantages: 1) Conductivity enhancers act as “secondary doping” or “conformation adjustment” agents. They can promote the transformation of conductive polymer chains from coiled cluster structures to more extended linear or network structures, greatly improving the charge transport efficiency within and between chains. This results in a significant reduction in the resistance of the printed devices.

[0093] 2) During the curing process, conductivity enhancers can regulate the phase separation behavior between the conductive phase and the resin phase, preventing excessive aggregation of conductive polymers and forming a more complete penetration network. Even with local defects, the overall conductive pathway remains stable. This improves the consistency of conductivity of the printed device at different locations and enhances its electrical stability under bending and stretching.

[0094] In some embodiments, the conductivity enhancer includes polyols and sugar alcohols, polar aprotic solvents, or ionic liquids.

[0095] As described above, polyols and sugar alcohols hardly volatilize during the heating of the printing platform or during long-term printing, resulting in stable slurry composition and consistent performance. The strong hydrogen bonding of polyols and sugar alcohols can enhance the toughness and interlayer bonding of the material, leading to better bending fatigue resistance in the printed devices (such as flexible circuits).

[0096] Polar aprotic solvents are low-viscosity liquids, which allow the conductive adhesive components to maintain good flowability and leveling. This ensures that the doctor blade can spread an extremely thin liquid layer with submicron-level flatness, thereby achieving high Z-axis resolution and a smooth surface in the printed device. If inefficient reinforcing agents are used, large amounts need to be added to achieve the same conductivity, leading to a surge in viscosity and making it impossible to print fine structures. Polar aprotic solvents have very weak absorption at commonly used ultraviolet wavelengths (such as 365nm and 405nm) and do not quench initiator free radicals. Therefore, ultraviolet light can penetrate the entire current printed layer with almost no attenuation, achieving full curing. This ensures that there will be no problems such as insufficient curing of the underlying layer or structural collapse due to light blockage, and high aspect ratio structures can be printed.

[0097] Ionic liquids introduce ionic pathways into polymer electronic conductive networks, making printed parts suitable for cutting-edge fields such as electrochemical sensing, energy storage (microcapacitors), and transistors. In addition, when combined with thermosetting resins of 2% or less in the formulation, ionic liquids can promote the formation of a denser cross-linked network during the later thermosetting process. Finally, the thermal and environmental stability of ionic liquids allows printed devices to operate stably in higher temperature or more humid environments, significantly improving reliability.

[0098] In addition, this application discloses the application of a second type of conductive adhesive in the fabrication of semiconductor devices by 3D printing.

[0099] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope. The scope of protection of the present invention is defined by the appended claims, specification, and their equivalents.

Claims

1. A conductive adhesive, characterized in that, The conductive adhesive comprises, by weight percentage: Conductive organic compounds: 5%-30%; Curable resin: 15%-30%; Solvent: 30%-70%.

2. The conductive adhesive according to claim 1, characterized in that, The conductive organic compounds include conductive polymers and their derivatives.

3. The conductive adhesive according to claim 2, characterized in that, The conductive polymeric compounds and their derivatives include at least one of PEDOT:PSS, polyaniline, polypyrrole and its derivatives.

4. The conductive adhesive according to claim 1, characterized in that, The curable resin includes at least one of photocurable resin and thermocurable resin; When the curable resin includes photocurable resin and thermocurable resin, 0% < photocurable resin ≤ 27%; 30% > thermocurable resin ≥ 3%.

5. The conductive adhesive according to claim 4, characterized in that, When the curable resin includes the photocurable resin, the conductive adhesive includes a photoinitiator, the proportion of which is 1%-3%; and / or, the photocurable resin includes epoxy acrylate or polyurethane acrylate. When the curable resin includes the thermosetting resin, the conductive adhesive includes a thermosetting agent, the proportion of which is 0.5%-4%, and / or the thermosetting resin includes a modified epoxy resin, a phenolic resin, or a polyimide precursor.

6. The conductive adhesive according to claim 1, characterized in that, The conductive adhesive includes a conductivity enhancer, and the proportion of the conductivity enhancer is 2%-7%.

7. The conductive adhesive according to claim 6, characterized in that, The conductivity enhancer includes polyols and sugar alcohols, polar aprotic solvents, or ionic liquids.

8. The conductive adhesive according to claim 1, characterized in that, The conductive adhesive includes an adhesion promoter, and the proportion of the adhesion promoter is 0.3%-1%.

9. The conductive adhesive according to claim 8, characterized in that, The adhesion promoter includes silanes, organotitanium / aluminum compounds, or polymeric surfactants.

10. The application of a conductive adhesive as described in any one of claims 1-9 in the manufacture of electronic devices.

11. The application according to claim 10, characterized in that, The application is to form a conductive connection structure between electronic components.

12. The application according to claim 10, characterized in that, The application is as a seed layer for electroplating on a semiconductor substrate or wafer.

13. The application according to claim 10, characterized in that, The application is to form transparent electrodes, electromagnetic shielding layers, or sensor sensitive layers.

14. A method for manufacturing a semiconductor device, characterized in that, Includes the following steps: (1) Provide a substrate; (2) Coating or printing the conductive adhesive as described in any one of claims 1-9 onto the target area of ​​the substrate; (3) The conductive adhesive is cured to form a conductive pattern; (4). Using the solidified conductive pattern as a seed layer for electroplating, an electroplating process is performed to form a metal interconnect structure.

15. The semiconductor device manufacturing method according to claim 14, characterized in that, Before or after the electroplating process, a photolithography process is also included on the substrate.

16. An electronic device, characterized in that, It includes at least one conductive structure formed by curing the conductive adhesive as described in any one of claims 1-9, the conductive structure being used to achieve electrical connections within or between devices.

17. A semiconductor device, characterized in that, include: Base; A conductive pattern layer formed by curing the conductive adhesive as described in any one of claims 1-9 is disposed on the substrate; as well as Metal interconnect structure disposed on the conductive pattern layer.

18. The semiconductor device according to claim 17, characterized in that: The conductive pattern layer serves as a seed layer for electroplating, and the metal interconnect layer is formed thereon through an electroplating process.

19. A conductive adhesive, characterized in that, The conductive adhesive comprises, by weight percentage: Conductive organic compounds: 5%-30%; Thermosetting resin: ≤2%; UV-curable resin: 50%-60%; Diluent: 35%-55%.

20. The conductive adhesive according to claim 19, characterized in that, The conductive organic compounds include conductive polymers and their derivatives.

21. The conductive adhesive according to claim 20, characterized in that, The conductive polymeric compounds and their derivatives include at least one of PEDOT:PSS, polyaniline, polypyrrole and its derivatives.

22. The conductive adhesive according to claim 19, characterized in that, The conductive adhesive includes a conductivity enhancer, and the proportion of the conductivity enhancer is 2%-7%.

23. The conductive adhesive according to claim 22, characterized in that, The conductivity enhancer includes polyols and sugar alcohols, polar aprotic solvents, or ionic liquids.

24. The use of the conductive adhesive according to any one of claims 19 to 23 in the fabrication of semiconductor devices by 3D printing.