Anisotropic conductive adhesive film with low pre-pasting temperature and preparation method thereof

Abstract

The invention belongs to the technical field of microelectronic packaging, and relates to an anisotropic conductive adhesive film with low pre-pasting temperature and a preparation method thereof. The surface performance of the special anisotropic conductive film (ACF) can be effectively improved by adopting a low-temperature plasma treatment technology, the bonding performance of the ACF and a substrate is further improved, working gas is ionized in a physical mode, plasma containing high-energy particles is generated, the high-energy particles collide with the surface of the ACF, the surface of the ACF is activated, and the surface of the ACF is activated. Compared with the prior art, the method has the advantages that the surface energy is increased, so that the bonding force between the ACF and the substrate is enhanced, the pre-pasting performance of the ACF can be remarkably improved on the premise that the chemical property of the ACF is not changed, the pre-pasting temperature of the ACF adhesive film in the using process is further reduced, and the problem of advanced curing caused by too high temperature is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of microelectronic packaging, and relates to an anisotropic conductive adhesive film with a low pre-lamination temperature and a preparation method thereof. Background Art

[0002] Anisotropic Conductive Film (ACF) is a material widely used in the field of electronic assembly, especially in microelectronic packaging technology. The uniqueness of ACF is that it can achieve electrical connection in the vertical direction while maintaining insulation in the horizontal direction, which makes it an ideal choice for connecting electronic components such as circuit boards, chips and displays. ACF contains conductive particles inside. When subjected to external pressure, these conductive particles will form a continuous conductive path in the vertical direction, thereby achieving circuit connection; at the same time, the non-conductive components in ACF ensure insulation in the horizontal direction, avoiding unnecessary short circuits.

[0003] In the process of microelectronic packaging, the pre-lamination of ACF is particularly important. Pre-lamination refers to applying a certain temperature and slight pressure between the ACF and the substrate to enhance the bonding strength between the ACF and the substrate. This process helps to ensure the smooth progress of subsequent operations. Typically, the pre-lamination process involves placing an ACF film with a polyethylene terephthalate (PET) protective film on the substrate and heating it. The purpose of heating is to activate the adhesive in the ACF so that it forms a preliminary bond with the substrate. Subsequently, the PET protective film can be smoothly peeled off from the surface of the ACF film, preparing for the subsequent pre-pressing and main pressing operations.

[0004] However, for some low-temperature ACF films, their curing temperature is relatively low, which brings new challenges to the pre-lamination process. If too high a temperature is used during the pre-lamination process, the ACF film may begin to cure before the main pressing. Once this happens, it will not only affect the bonding quality between the ACF and the substrate, but may also cause the conductive properties of the ACF to be damaged, thereby affecting the performance of the final product. In order to avoid this risk, measures need to be taken to reduce the pre-lamination temperature of the ACF film. Summary of the invention

[0005] The purpose of the present invention is to address the above problems existing in the prior art and propose an anisotropic conductive adhesive film that can achieve a low pre-lamination temperature of 40°C, and to increase the surface energy of the anisotropic conductive adhesive film through warm plasma treatment technology to improve its bonding performance with the substrate.

[0006] The purpose of the present invention can be achieved by the following technical scheme: a low pre-lamination temperature anisotropic conductive adhesive film, the anisotropic conductive adhesive film comprising the following raw materials in parts by weight: 15-30 parts of epoxy resin E51, 10-20 parts of conductive particles, 10-20 parts of alicyclic epoxy monomers, 0.1-10 parts of curing agent, and 5-10 parts of silicon dioxide.

[0007] In the above-mentioned anisotropic conductive adhesive film with low pre-lamination temperature, the curing agent is at least two of benzylmethyl hydroxyphenylsulfonium hexafluorophosphate, boron trifluoride, and aluminum trichloride.

[0008] In the above-mentioned low pre-lamination temperature anisotropic conductive adhesive film, the curing agent is benzylmethyl hydroxyphenyl sulfonium hexafluorophosphate, boron trifluoride and aluminum trichloride in a mass ratio of 1: (0.5-1.5): (0.5-1.5). The present invention adopts low-temperature plasma treatment technology to effectively improve the surface properties of the anisotropic conductive adhesive film (ACF), thereby improving its bonding performance with the substrate. The working gas is ionized to generate a low-temperature plasma containing high-energy particles (such as electrons, ions, etc.). These high-energy particles collide with the surface of the ACF, so that the ACF surface is activated, the surface energy is increased, and thus the bonding force between the ACF and the substrate is improved. In particular, when a curing agent is used that is a system consisting of benzylmethyl hydroxyphenylsulfonium hexafluorophosphate, boron trifluoride and aluminum trichloride in a mass ratio of 1:(0.5-1.5):(0.5-1.5), since this cationic curing reaction has high efficiency and low reaction temperature, the need to achieve pre-lamination by increasing the machine temperature is avoided, as the latter has the risk of premature curing of the film. By utilizing low-temperature plasma treatment technology, not only can good bonding effect of ACF at a lower temperature be ensured, but also the occurrence of pre-curing can be effectively prevented, thereby ensuring the stability and reliability of the ACF film in practical applications.

[0009] In the above-mentioned low pre-lamination temperature anisotropic conductive adhesive film, the conductive particles are PS-Ni powder with a particle size of 3-8 μm. The present invention controls the particle size of nano nickel (Ni) particles (PS-Ni powder) loaded by polystyrene (PS) microspheres to be 3-8 μm. The conductive particles in this particle size range are very suitable for small spacing lamination and can be tightly filled in tiny circuit gaps, thereby ensuring efficient and stable connection between high-density circuits.

[0010] Preferably, the particle size of the silicon dioxide is 185-210 nm.

[0011] In the above-mentioned anisotropic conductive adhesive film with a low pre-lamination temperature, the alicyclic epoxy monomer is an alicyclic epoxy monomer S-06E. The alicyclic epoxy monomer S-06E has the characteristics of rapid curing, and the polymer formed after curing has a higher modulus. However, this also means that if the pre-lamination temperature is set too high, S-06E may undergo a curing reaction in advance, which will affect the subsequent processing of the ACF film. Therefore, the present invention uses low-temperature plasma treatment technology to achieve ACF pre-lamination at a lower temperature without causing premature curing of S-06E, thereby ensuring the smooth progress of subsequent pressing operations; in addition, S-06E can also improve the fluidity of the ACF mixture, which helps the conductive particles to be more evenly dispersed in the ACF, thereby improving the overall performance of the ACF; finally, the addition of S-06E helps to optimize the curing behavior of the entire ACF system, and at the same time, in conjunction with other raw materials and plasma treatment technology, a good pre-lamination effect can be obtained, avoiding the problem of premature curing.

[0012] The present invention also provides a method for preparing the above-mentioned anisotropic conductive adhesive film with low pre-lamination temperature, the method comprising the following steps:

[0013] S1, prepare the above raw materials;

[0014] S2, stirring the epoxy resin, conductive particles, alicyclic epoxy monomer and silicon dioxide, and then adding a curing agent and continuing to stir to obtain a coating liquid;

[0015] S3, coating the coating liquid into a film and then performing a heating treatment to obtain an ACF prefabricated film;

[0016] S4. Perform low-temperature plasma treatment on the ACF prefabricated adhesive film to obtain an anisotropic conductive adhesive film with a low pre-lamination temperature.

[0017] In the above-mentioned method for preparing anisotropic conductive adhesive film with low pre-lamination temperature, the heating treatment temperature in step S3 is 65-75° C. and the time is 1-5 min.

[0018] In the above-mentioned method for preparing anisotropic conductive adhesive film with low pre-lamination temperature, the low-temperature plasma treatment temperature in step S4 is 5-10° C. The present invention can effectively avoid ACF pre-curing caused by excessive temperature by accurately controlling the plasma treatment temperature to 5-10° C. The pre-curing will cause the bonding strength between the ACF and the substrate to decrease, directly affecting the connection quality and durability of the final product, and will cause insufficient formation of the conductive path, thereby affecting the conductive performance of the circuit.

[0019] In the above-mentioned method for preparing anisotropic conductive adhesive film with low pre-lamination temperature, the working gas in the low-temperature plasma treatment process of step S4 is argon or nitrogen, the flow rate is 10-50sccm, and the vacuum degree is 0.5-1.5×10-3 Torr.

[0020] In the above-mentioned method for preparing anisotropic conductive adhesive film with low pre-lamination temperature, the power of low-temperature plasma treatment in step S4 is 100-1000W, and the treatment time is 3-5min.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention adopts low-temperature plasma treatment technology to effectively improve the surface properties of the special anisotropic conductive film (ACF) of the present invention, thereby improving its bonding performance with the substrate, and then ionizes the working gas by physical means to generate plasma containing high-energy particles. These high-energy particles collide with the surface of the ACF, activate its surface, increase the surface energy, and thus enhance the bonding force between the ACF and the substrate. In this way, the pre-lamination performance of the ACF can be significantly improved without changing the chemical properties of the ACF, thereby reducing the pre-lamination temperature of the ACF film during use, and avoiding the problem of premature curing caused by excessively high temperature. DETAILED DESCRIPTION

[0023] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0024] Embodiment 1:

[0025] S1, prepare the following raw materials: 18 parts of epoxy resin E51, 16 parts of conductive particles, 13 parts of alicyclic epoxy monomer S-06E, 3 parts of curing agent, and 8 parts of silicon dioxide with a particle size of 200 nm;

[0026] The conductive particles are PS-Ni powder with a particle size of 5 μm, and the curing agent is benzylmethyl hydroxyphenylsulfonium hexafluorophosphate, boron trifluoride and aluminum trichloride in a mass ratio of 1:1:1;

[0027] S2, stirring epoxy resin E51, conductive particles, alicyclic epoxy monomer S-06E and silicon dioxide, and then adding a curing agent and continuing to stir to obtain a coating liquid;

[0028] S3, coating the coating liquid into a film and then heating it at 70° C. for 3 min to obtain an ACF prefabricated film;

[0029] S4, set the temperature of the low-temperature plasma treatment equipment to 8°C, put the ACF film (width: 500mm) into the reaction chamber of the plasma treatment equipment, close the reaction chamber door, and evacuate to a vacuum degree of 10 -3 Torr;

[0030] S5, introduce nitrogen as working gas into the reaction chamber at a flow rate of 30 sccm, and maintain the vacuum degree at 10 -3 Torr; turn on the RF power supply, adjust the power level to 300W, and the processing time is 3 minutes. During this process, the working gas is ionized under the action of the RF electric field to generate high-energy particles (such as electrons, ions, etc.). These high-energy particles collide with the surface of the anisotropic conductive film (ACF) to be processed, activating its surface, thereby increasing the adhesion between the ACF film and the substrate surface, thereby reducing the pre-lamination temperature;

[0031] S6. After the treatment is completed, turn off the RF power supply and the argon gas supply, open the reaction chamber door, and take out the treated anisotropic conductive film (ACF).

[0032] S7. The peeling force of the ACF and the substrate at the same temperature before and after the test and the minimum pre-lamination temperature that meets the pre-lamination requirements are evaluated to evaluate the degree of improvement of the pre-lamination performance; during the pre-lamination process, the knife head is pressed down for 1s and the pressure is 1MPa.

[0033] Embodiment 2:

[0034] S1, prepare the following raw materials: 15 parts of epoxy resin E51, 10 parts of conductive particles, 10 parts of alicyclic epoxy monomer S-06E, 0.1 parts of curing agent, and 5 parts of silicon dioxide with a particle size of 200 nm;

[0035] The conductive particles are PS-Ni powder with a particle size of 5 μm, and the curing agent is benzylmethyl hydroxyphenylsulfonium hexafluorophosphate, boron trifluoride and aluminum trichloride in a mass ratio of 1:1:1;

[0036] S2, stirring epoxy resin E51, conductive particles, alicyclic epoxy monomer S-06E and silicon dioxide, and then adding a curing agent and continuing to stir to obtain a coating liquid;

[0037] S3, coating the coating liquid into a film and then heating it at 70° C. for 3 min to obtain an ACF prefabricated film;

[0038] S4, set the temperature of the low-temperature plasma treatment equipment to 8°C, put the ACF film (width: 500mm) into the reaction chamber of the plasma treatment equipment, close the reaction chamber door, and evacuate to a vacuum degree of 10 -3 Torr;

[0039] S5, introduce nitrogen as working gas into the reaction chamber at a flow rate of 30 sccm, and maintain the vacuum degree at 10 -3Torr; turn on the RF power supply, adjust the power level to 300W, and the processing time is 3 minutes. During this process, the working gas is ionized under the action of the RF electric field to generate high-energy particles (such as electrons, ions, etc.). These high-energy particles collide with the surface of the anisotropic conductive film (ACF) to be processed, activating its surface, thereby increasing the adhesion between the ACF film and the substrate surface, thereby reducing the pre-lamination temperature;

[0040] S6. After the treatment is completed, turn off the RF power supply and the argon gas supply, open the reaction chamber door, and take out the treated anisotropic conductive film (ACF).

[0041] S7. The peeling force of the ACF and the substrate at the same temperature before and after the test and the minimum pre-lamination temperature that meets the pre-lamination requirements are evaluated to evaluate the degree of improvement of the pre-lamination performance; during the pre-lamination process, the knife head is pressed down for 1s and the pressure is 1MPa.

[0042] Embodiment 3:

[0043] S1, prepare the following raw materials: 30 parts of epoxy resin E51, 20 parts of conductive particles, 20 parts of alicyclic epoxy monomer S-06E, 10 parts of curing agent, and 10 parts of silicon dioxide with a particle size of 200 nm;

[0044] The conductive particles are PS-Ni powder with a particle size of 5 μm, and the curing agent is benzylmethyl hydroxyphenylsulfonium hexafluorophosphate, boron trifluoride and aluminum trichloride in a mass ratio of 1:1:1;

[0045] S2, stirring epoxy resin E51, conductive particles, alicyclic epoxy monomer S-06E and silicon dioxide, and then adding a curing agent and continuing to stir to obtain a coating liquid;

[0046] S3, coating the coating liquid into a film and then heating it at 70° C. for 3 min to obtain an ACF prefabricated film;

[0047] S4, set the temperature of the low-temperature plasma treatment equipment to 8°C, put the ACF film (width: 500mm) into the reaction chamber of the plasma treatment equipment, close the reaction chamber door, and evacuate to a vacuum degree of 10 -3 Torr;

[0048] S5, introduce nitrogen as working gas into the reaction chamber at a flow rate of 30 sccm, and maintain the vacuum degree at 10 -3 Torr; turn on the RF power supply, adjust the power level to 300W, and the processing time is 3 minutes. During this process, the working gas is ionized under the action of the RF electric field to generate high-energy particles (such as electrons, ions, etc.). These high-energy particles collide with the surface of the anisotropic conductive film (ACF) to be processed, activating its surface, thereby increasing the adhesion between the ACF film and the substrate surface, thereby reducing the pre-lamination temperature;

[0049] S6. After the treatment is completed, turn off the RF power supply and the argon gas supply, open the reaction chamber door, and take out the treated anisotropic conductive film (ACF).

[0050] S7. The peeling force of the ACF and the substrate at the same temperature before and after the test and the minimum pre-lamination temperature that meets the pre-lamination requirements are evaluated to evaluate the degree of improvement of the pre-lamination performance; during the pre-lamination process, the knife head is pressed down for 1s and the pressure is 1MPa.

[0051] Embodiment 4:

[0052] The only difference from Example 1 is that the amount of silicon dioxide added is 15 parts.

[0053] Embodiment 5:

[0054] The only difference from Example 1 is that the amount of silicon dioxide added is 1 part.

[0055] Embodiment 6:

[0056] The only difference from Example 1 is that the amount of conductive particles added is 25 parts.

[0057] Embodiment 7:

[0058] The only difference from Example 1 is that the amount of conductive particles added is 5 parts.

[0059] Embodiment 8:

[0060] The only difference from Example 1 is that in step S5, the RF power source is turned on and the power level is adjusted to 100W.

[0061] Embodiment 9:

[0062] The only difference from Example 1 is that the curing agent is 2-ethyl-4-methylimidazole

[0063] Comparative Example 1:

[0064] The only difference from Example 1 is that the S4-S6 low-temperature plasma treatment is not performed.

[0065] Comparative Example 2:

[0066] The only difference from Example 1 is that the epoxy resin E51 is replaced by the epoxy resin E44.

[0067] Comparative Example 3:

[0068] The only difference from Example 1 is that the alicyclic epoxy monomer S-06E is replaced by bisphenol A diglycidyl ether.

[0069] Table 1: Performance test results of anisotropic conductive adhesive films prepared in Examples 1-8 and Comparative Examples 1-3

[0070]

[0071]

[0072] In summary, the present invention uses low-temperature plasma treatment technology to effectively improve the surface properties of the special anisotropic conductive film (ACF) of the present invention, thereby improving its bonding performance with the substrate. The present invention ionizes the working gas by physical means to generate a plasma containing high-energy particles. These high-energy particles collide with the surface of the ACF, activate its surface, increase the energy of the surface, and thus enhance the bonding force between the ACF and the substrate. In this way, the pre-lamination performance of the ACF can be significantly improved without changing the chemical properties of the ACF, thereby reducing the pre-lamination temperature of the ACF film during use, avoiding the problem of premature curing due to excessively high temperature.

[0073] The parts of the embodiments herein that are not exhaustive of the midpoint values ​​of the technical scope claimed for protection by the present invention and the new technical solutions formed by equivalent replacement of single or multiple technical features in the technical solutions of the embodiments are also within the scope claimed for protection by the present invention; at the same time, in all the listed or unlisted embodiments of the scheme of the present invention, each parameter in the same embodiment merely represents an example of its technical solution (i.e., a feasible solution), and there is no strict coordination and limitation relationship between the parameters, wherein the parameters can be replaced with each other without violating the axioms and the claims of the present invention, unless otherwise stated.

[0074] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical schemes composed of any combination of the above technical features. The above is a specific implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

[0075] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A low pre-lamination temperature anisotropic conductive adhesive film, characterized in that: The anisotropic conductive adhesive film comprises the following raw materials in parts by mass: 15-30 parts of epoxy resin E51, 10-20 parts of conductive particles, 10-20 parts of alicyclic epoxy monomers, 0.1-10 parts of curing agent, and 5-10 parts of silicon dioxide.

2. The low pre-lamination temperature anisotropic conductive adhesive film according to claim 1, characterized in that: The curing agent is at least two of benzylmethylhydroxyphenylsulfonium hexafluorophosphate, boron trifluoride, and aluminum trichloride.

3. The anisotropic conductive adhesive film with a low pre-lamination temperature according to claim 2, characterized in that: The curing agent is benzylmethyl hydroxyphenylsulfonium hexafluorophosphate, boron trifluoride and aluminum trichloride in a mass ratio of 1: (0.5-1.5): (0.5-1.5).

4. The anisotropic conductive adhesive film with a low pre-lamination temperature according to claim 1, characterized in that: The conductive particles are PS-Ni powder with a particle size of 3-8 μm.

5. The anisotropic conductive adhesive film with low pre-lamination temperature according to claim 1, characterized in that: The alicyclic epoxy monomer is alicyclic epoxy monomer S-06E.

6. A method for preparing anisotropic conductive adhesive film with low pre-lamination temperature as claimed in claim 1, characterized in that: The method comprises the following steps: S1. Prepare the raw materials according to claim 1; S2, stirring the epoxy resin, conductive particles, alicyclic epoxy monomer and silicon dioxide, then adding a curing agent and continuing to stir to obtain a coating liquid; S3, coating the coating liquid into a film and then heating it to obtain an ACF prefabricated film; S4. The ACF prefabricated adhesive film is subjected to low-temperature plasma treatment to obtain an anisotropic conductive adhesive film with a low pre-lamination temperature.

7. The method for preparing anisotropic conductive adhesive film with low pre-lamination temperature according to claim 6, characterized in that: In step S3, the heating treatment temperature is 65-75° C. and the time is 1-5 minutes.

8. The method for preparing anisotropic conductive adhesive film with low pre-lamination temperature according to claim 6, characterized in that: The temperature of the low-temperature plasma treatment in step S4 is 5-10°C.

9. The method for preparing anisotropic conductive adhesive film with low pre-lamination temperature according to claim 6, characterized in that: In step S4, the working gas during the low-temperature plasma treatment is argon or nitrogen, with a flow rate of 10-50 sccm and a vacuum degree of 0.5-1.5×10 -3 Torr.

10. The method for preparing anisotropic conductive adhesive film with low pre-lamination temperature according to claim 6, characterized in that: In step S4, the low-temperature plasma treatment power is 100-1000W, and the treatment time is 3-5 minutes.

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