A cushioning material for ACF attachment and a method for manufacturing the same

Abstract

The application discloses a kind of buffer material for ACF attachment and its preparation method, belong to semiconductor packaging technical field.The buffer material described in the application is sequentially polyimide / silicone rubber composite material, silicone rubber and polyimide / silicone rubber composite material from top to bottom.The polyamide acid nanofiber membrane is prepared by electrospinning in the application;Methylated fumed silica, modified boron nitride and fluorosilicone are mixed and dispersed to obtain a first mixed solution;Platinum catalyst is dispersed in fluorosilicone to obtain a second mixed solution;After the first mixed solution and the second mixed solution are mixed evenly, dimethylacetamide is added for dilution to prepare a silicone rubber infiltration solution.The polyamide acid nanofiber membrane is immersed in the silicone rubber infiltration solution, vacuum infiltration treatment is carried out, and then gradient temperature treatment is carried out to obtain the polyimide / silicone rubber composite material.Finally, the polyimide / silicone rubber composite material and the silicone rubber are sequentially laminated, and the buffer material is prepared by vacuum hot pressing treatment.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor packaging technology and relates to a buffer material for ACF bonding and pressing and its preparation method. Background Technology

[0002] In the manufacturing process of flat panel displays such as liquid crystal displays (LCDs) and organic light-emitting diode displays (OLEDs), the anisotropic conductive film (ACF) lamination and pressing process is one of the key steps to achieve reliable electrical connections between driver chips (ICs), flexible printed circuit boards (FPCs), and display panel terminals. This process uses a hot press head to apply specific temperature, pressure, and time-dependent hot pressing, which allows the conductive particles in the ACF to effectively conduct electricity between the upper and lower electrodes, while simultaneously curing the insulating resin to achieve a permanent mechanical and electrical connection.

[0003] To ensure uniform pressure transmission during hot pressing, protect panel terminals from mechanical damage, and improve ACF adhesion quality, existing technologies commonly incorporate a buffer material between the hot pressing head and the components to be pressed, with hot pressing silicone pads being the most widely used. However, in actual production, after repeated high-temperature and high-pressure cycles, the internal molecular chains of the hot pressing silicone pads are prone to breakage, leading to cracks, chipping, and damage. This phenomenon gradually worsens with each pressing cycle. This is because the cross-linked structure of the silicone material is destroyed under repeated thermomechanical stress, resulting in decreased toughness, increased brittleness, and ultimately, loss of its buffering function.

[0004] The loss of buffering function further leads to various process defects, thereby reducing product yield. Specifically, surface cracks and debris in the buffer material can cause uneven pressure distribution, resulting in ACF attachment position misalignment, air bubble residue, or weak adhesion, affecting the quality of subsequent bonding processes. Tiny particles generated by buffer material debris can mix into the ACF layer or electrode contact area as foreign matter, causing abnormal distribution of conductive particles and leading to electrical connection failure or short circuit risk. After the buffer material is damaged, the pressure of the hot press head cannot be effectively buffered and acts directly on the panel terminals, causing terminal deformation, scratches, or even breakage, resulting in the scrapping of the display panel.

[0005] The aforementioned process defects directly lead to a significant reduction in the production FPY (First Pass Yield). At the same time, the cushioning material needs to be replaced frequently, and the costs of manual screening and rework also increase. This not only reduces production efficiency but also significantly increases raw material consumption and manufacturing costs, seriously affecting the company's economic benefits and market competitiveness. Summary of the Invention

[0006] To address the problems and deficiencies in the prior art, this invention provides a cushioning material for ACF (Acrylic Fluid Fabric) attachment and its preparation method.

[0007] In a first aspect, the present invention provides a cushioning material for ACF (Acrylic Fluidized Fork) attachment and pressing, the cushioning material having a three-layer structure, consisting of a polyimide / silicone rubber composite material, silicone rubber, and a polyimide / silicone rubber composite material from top to bottom;

[0008] The polyimide / silicone rubber composite material uses a polyimide fiber skeleton as a reinforcing structure, and silicone rubber fills and coats the polyimide nanofiber skeleton to form an interpenetrating network structure. The silicone rubber is a hot-pressed silicone rubber, and its upper and lower surfaces are tightly bonded to a polyimide / silicone rubber composite material, respectively.

[0009] Furthermore, in the cushioning material for ACF bonding provided by the present invention, the thickness of the polyimide / silicone rubber composite material is 0.05~0.1mm; The thickness of the silicone rubber is 0.2~0.25mm.

[0010] In a second aspect, the present invention provides a method for preparing a cushioning material for ACF (Acrylic Fluidized Coating) bonding, comprising: sequentially stacking a polyimide / silicone rubber composite material, a silicone rubber and a polyimide / silicone rubber composite material, and then subjecting them to vacuum hot pressing to obtain the cushioning material; The vacuum hot pressing process is performed at a temperature of 150~180℃ for 20~30 minutes.

[0011] Furthermore, in the preparation method of the cushioning material for ACF adhesion and pressing provided by the present invention, the preparation of the polyimide / silicone rubber composite material includes: preparing a polyamic acid nanofiber membrane by electrospinning; mixing and dispersing methylated fumed silica, modified boron nitride and fluorosilicone to obtain a first mixture; dispersing a platinum catalyst in fluorosilicone to obtain a second mixture; mixing the first mixture and the second mixture evenly, and then adding dimethylacetamide for dilution to obtain a silicone rubber infiltration solution; immersing the polyamic acid nanofiber membrane in the silicone rubber infiltration solution, performing vacuum infiltration treatment, and then performing gradient heating treatment to obtain the polyimide / silicone rubber composite material.

[0012] Furthermore, in the preparation method of the buffer material for ACF attachment and pressing provided by the present invention, the electrospinning process conditions are: voltage 15~20kV, receiving distance 10~15cm, spinning rate 0.5~1mL / h, and spinning time 1~2h. The solid content of polyamic acid in the spinning solution used for electrospinning is 12%~15%.

[0013] Furthermore, in the preparation method of the buffer material for ACF adhesion and pressing provided by the present invention, the first mixture comprises, by mass parts: 600-800 parts of methylated fumed silica, 200-400 parts of modified boron nitride, and 9400-11400 parts of fluorosilicone. The second mixture comprises: 7-10 parts platinum catalyst and 80-100 parts fluorosilicone; The platinum catalyst is a 2% Karstedt catalyst.

[0014] Furthermore, in the preparation method of the buffer material for ACF bonding and pressing provided by the present invention, the preparation method of the modified boron nitride includes: surface modification treatment of boron nitride using a silane coupling agent; The method for preparing methylated fumed silica includes: surface modification treatment of fumed silica using a methylating agent.

[0015] Furthermore, in the preparation method of the buffer material for ACF adhesion and pressing provided by the present invention, the vacuum permeation treatment time is 30~60 min.

[0016] Furthermore, in the preparation method of the cushioning material for ACF adhesion and pressing provided by the present invention, under nitrogen protection, the temperature is increased to 50-80℃ at 2-3℃ / min and held for 0.5-1h, increased to 100-120℃ at 2-3℃ / min and held for 0.5-1h, increased to 150-180℃ at 1.5-2℃ / min and held for 1-2h, and increased to 300-350℃ at 1-1.5℃ / min and held for 1-2h.

[0017] Thirdly, the present invention provides the application of cushioning materials for ACF bonding in connecting flexible circuit boards and printed circuit boards, glass substrates and driver chips, or thin-film flip-chip packages.

[0018] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: (1) In this invention, an uniminolated polyamic acid nanofiber membrane is immersed in a silicone rubber infiltration solution. Under the action of the diluent dimethylacetamide, the surface of the polyamic acid nanofiber undergoes moderate swelling, and the molecular chain mobility is enhanced, allowing small molecules and oligomers in the silicone rubber to infiltrate into the surface region of the polyamic acid nanofiber. During the gradient heating process, the crosslinking and curing of the silicone rubber and the thermal iminolation of the polyamic acid proceed simultaneously. Since the iminolation shrinkage of the polyimide occurs after the silicone rubber has been cured and shaped, the shrinkage tendency of the polyimide fiber is limited by the surrounding silicone rubber matrix. The polyimide fiber cannot shrink as a whole, but can only form a tight physical entanglement with the silicone rubber matrix at the molecular chain level and produce local chemical bonds. Finally, the polyimide fiber skeleton and the silicone rubber two phases form an interpenetrating network structure in three-dimensional space. Among them, the polyimide fiber skeleton bears the main compressive stress, preventing excessive deformation of the polyimide / silicone rubber composite material; the silicone rubber absorbs the compressive deformation and provides elastic recovery force, ensuring that the buffer material maintains stable pressure transmission performance during repeated hot-pressing cycles.

[0019] (2) The S-PI / SR buffer material prepared by the present invention has the characteristics of uniform pressure, good thermal conductivity, non-sticking to ACF (good release property) and antistatic properties, which can fully meet the performance requirements of the ACF bonding and pressing process for the buffer material.

[0020] (3) The maximum number of pressing cycles for commercially available hot-pressed silicone sheets is 200, while the maximum number of pressing cycles for the S-PI / SR buffer material of this invention can reach 1800, an increase of 800%, and the material cost can be reduced by about 800%, which greatly reduces the material consumption cost of the ACF bonding pressing process.

[0021] (4) The Bonding equipment is set to stop and replace the cushioning material when the number of presses reaches the upper limit, and the replacement time is 2 minutes. After adopting the S-PI / SR cushioning material of this invention, the upper limit of the number of presses is increased from 200 times to 1800 times. The time of production capacity impact caused by replacing the cushioning material under single-shift production capacity is reduced by about 88.9%, which significantly improves equipment utilization and production efficiency.

[0022] (5) After using the S-PI / SR buffer material of the present invention, the total foreign matter defect rate of the OLB Bonding process decreased from 0.07% to 0.04%; among which, the black shaving foreign matter defect rate directly related to the wear and shedding of the buffer material decreased from 0.03% to 0%. The present invention can effectively inhibit the crack initiation and debris shedding of the buffer material during repeated hot pressing cycles, thereby significantly improving the cleanliness and product yield of the ACF bonding process. Attached Figure Description

[0023] Figure 1 This is a trend chart showing the foreign matter defects in OLB after using S-PI / SR-1.

[0024] Figure 2 This is a trend chart showing the decline of black foreign matter defects in OLB after using S-PI / SR-1. Detailed Implementation

[0025] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials can be purchased commercially.

[0026] Example 1 This embodiment provides a method for preparing a polyimide (PI) / silicone rubber (SR) composite material.

[0027] The preparation method described in this embodiment is as follows: (1) Preparation of polyamic acid nanofiber membrane: Under nitrogen protection, 0.6 mol TFDB (2,2'-di(trifluoromethyl)diaminobiphenyl) was dissolved in 1000 mL DMAc (dimethylacetamide), and then 0.3 mol 6FDA (4,4'-(hexafluoroisopropene)phthalic anhydride) and 0.3 mol BPDA (3,3',4,4'-biphenyltetracarboxylic dianhydride) were added. The mixture was stirred for 24 h to obtain a PAA (polyamic acid) solution. 7 mL of the PAA solution was mixed with 10 mL of DMAc to obtain a spinning solution (PAA solid content was 15%). The spinning solution was electrospun at a voltage of 15 kV, the distance from the syringe needle tip to the receiving device was 15 cm, the electrospinning speed was 0.5 mL / h, and the electrospinning time was 2 h to prepare a polyamic acid (PAA) nanofiber membrane.

[0028] (2) Preparation of silicone rubber infiltration solution: 2.00 g of dried fumed silica (Hubei Huifu Nanomaterials Co., Ltd., HL-150) was ultrasonically dispersed in 60 mL of anhydrous ethanol, and then 8 mL of hexamethyldisilazane (HMDS) was added. The mixture was stirred at 120 °C for 3 h. After the reaction was completed, the mixture was centrifuged and washed three times with an ethanol solution (ethanol:water = 1:1, v / v) to obtain methylated fumed silica.

[0029] Under 60℃ water bath conditions, 0.4g of silane coupling agent (KH-550) was dissolved in 20mL of water, and then 4g of boron nitride (BN) was added. The mixture was stirred and reacted for 4h to obtain modified boron nitride.

[0030] 6g of methylated fumed silica and 4g of modified boron nitride were added to 99g of fluorosilicone and dispersed at 5000rpm for 20min. Then, 30g of hydrogen-containing silicone oil was added and stirred for 10min to obtain the first mixture. 70mg of platinum catalyst (2% Karstedt catalyst) was dispersed in 1g of fluorosilicone to obtain the second mixture. The first and second mixtures were mixed thoroughly, and 10mL of DMAc was added. After stirring and mixing thoroughly, the mixture was placed in a vacuum environment for 10min to obtain the silicone rubber infiltration solution.

[0031] (3) Preparation of polyimide / silicone rubber composite material: The PAA nanofiber membrane was cut into rectangles of 8cm×4cm and immersed in 40mL of silicone rubber infiltration solution. The membrane was then evacuated for 30min to allow the dispersion to fully infiltrate the PAA nanofiber membrane, thus obtaining a composite nanofiber membrane. Excess silicone rubber infiltration solution was scraped off the surface of the composite nanofiber membrane with a scraper. The membrane was then placed in a tube furnace and heated to 80℃ at 3℃ / min and held for 1h under nitrogen protection. The temperature was then increased to 120℃ at 3℃ / min and held for 1h. The temperature was then increased to 150℃ at 2℃ / min and held for 1h. Finally, the temperature was increased to 300℃ at 1℃ / min and held for 1h to obtain the PI / SR composite material.

[0032] Example 2 The method for preparing the PI / SR composite material in this embodiment is the same as in Embodiment 1, except that the electrospinning time for preparing the PAA nanofiber membrane in this embodiment is 1 hour. The preparation of the silicone rubber infiltration solution includes: adding 7g of methylated fumed silica and 2g of modified boron nitride to 114g of fluorosilicone, dispersing at 5000rpm for 10min, then adding 25g of hydrogen-containing silicone oil and stirring for 5min to obtain a first mixture. Dispersing 100mg of platinum catalyst (2% Karstedt catalyst) in 1g of fluorosilicone to obtain a second mixture. Mixing the first and second mixtures thoroughly, adding 5mL of DMAc, stirring until homogeneous, and then placing in a vacuum environment for 10min to obtain the silicone rubber infiltration solution.

[0033] Example 3 The method for preparing the PI / SR composite material in this embodiment is the same as in Embodiment 1, except that the electrospinning time for preparing the PI nanofiber membrane in this embodiment is 1.5 h. The preparation of the silicone rubber infiltration solution includes: adding 8g of methylated fumed silica and 3g of modified boron nitride to 94g of fluorosilicone, dispersing at 5000rpm for 10min, then adding 20g of hydrogen-containing silicone oil and stirring for 5min to obtain a first mixture. Dispersing 90mg of platinum catalyst (2% Karstedt catalyst) in 1g of fluorosilicone to obtain a second mixture. Mixing the first and second mixtures thoroughly, adding 8mL of DMAc, stirring until homogeneous, and then placing in a vacuum environment for 10min to obtain the silicone rubber infiltration solution.

[0034] Comparative Example 1 The preparation method of the SR composite material in this comparative example includes: coating the silicone rubber infiltration liquid prepared in Example 1 onto the surface of a flat plate, then placing it in a tube furnace, and heating it to 80°C at 3°C / min and holding it for 1 hour under nitrogen protection, heating it to 120°C at 3°C / min and holding it for 1 hour, and heating it to 150°C at 2°C / min and holding it for 1 hour to obtain the SR composite material.

[0035] Comparative Example 2 The preparation method of the PI / SR composite material in this comparative example includes: placing the PAA nanofiber membrane prepared in Example 1 in a tube furnace, heating to 150°C and holding for 30 min under nitrogen protection, heating to 250°C and holding for 30 min, and finally heating to 300°C and holding for 1 h to obtain a polyimide (PI) nanofiber membrane. The PI nanofiber membrane is cut into rectangles of 8 cm × 4 cm and immersed in the silicone rubber infiltration solution (40 mL) prepared in Example 1. Vacuum is applied for 30 min to allow the dispersion to fully infiltrate the PI nanofiber membrane, thus obtaining a composite nanofiber membrane. Excess silicone rubber infiltration liquid on the surface of the composite nanofiber membrane was scraped off with a scraper. Then, the membrane was placed in a tube furnace and heated to 80°C at 3°C / min and held for 1 hour under nitrogen protection. The temperature was then increased to 120°C at 3°C / min and held for 1 hour. The temperature was then increased to 150°C at 2°C / min and held for 1 hour. Finally, the temperature was increased to 300°C at 1°C / min and held for 1 hour to obtain the PI / SR composite material.

[0036] Comparative Example 3 This comparative example is the same as Example 1, except that in this comparative example, the PAA nanofiber membrane was immersed in 40 mL of silicone rubber infiltration solution for 30 min to obtain the PI / SR composite material.

[0037] Example 4 This embodiment provides a cushioning material for ACF (Acrylic Fluid Fabric) attachment and its preparation method.

[0038] The cushioning material (S-PI / SR-1) described in this embodiment has a three-layer structure, consisting of PI / SR composite material, hot-pressed silicone skin, and PI / SR composite material from top to bottom.

[0039] The preparation method includes: sequentially stacking the PI / SR composite material obtained in Example 1, hot-pressed silicone rubber (manufactured by Shin-Etsu Chemical Industry Co., Ltd., Japan, HC-20A, 0.2mm) and the PI / SR composite material, placing them in a vacuum hot press, and hot-pressing them at 150°C for 30 minutes under vacuum conditions, and then naturally cooling them to obtain the buffer material.

[0040] Example 5 The cushioning material (S-PI / SR-2) described in this embodiment is the same as that in Embodiment 4, except that the PI / SR composite material in this embodiment is prepared from Embodiment 2.

[0041] Example 6 The cushioning material (S-PI / SR-3) described in this embodiment is the same as that in embodiment 4, except that the PI / SR composite material in this embodiment is prepared from embodiment 3.

[0042] Comparative Example 4 The cushioning material (S-SR) described in this comparative example is the same as that in Example 4, except that the PI / SR composite material in Example 4 is replaced with the SR composite material in Comparative Example 1.

[0043] Comparative Example 5 The cushioning material (S-PI / SR-4) described in this comparative example is the same as that in Example 4, except that the PI / SR composite material in this example is prepared from Comparative Example 2.

[0044] Comparative Example 6 The cushioning material (S-PI / SR-5) described in this comparative example is the same as that in Example 4, except that the PI / SR composite material in this example was prepared from Comparative Example 3.

[0045] The hardness of the cushioning material (S-PI / SR) was tested according to GB / T 39693.4-2025 standard.

[0046] The thermal conductivity of the cushioning material was tested according to ASTM D5470 standard.

[0047] The volume resistivity of the buffer material was tested according to GB / T 1410-2006 standard.

[0048] The cushioning material was assembled onto an ACF hot press and subjected to repeated compression cycle tests according to the ACF bonding standard process conditions. The compression conditions were: temperature 180±5℃, pressure 30~40 kg / cm². 2 The pressing time is 15 seconds. After every 100 cycles, the cushioning material is removed, the surface morphology of the material is observed, and the number of cycles at which the first crack, chipping, or obvious damage occurs is recorded. This number is the pressing life.

[0049] Place the pressure-sensitive paper (Fuji Prescale film) between the hot press head and the part to be pressed, and place the buffer material to be tested underneath. Press according to the ACF pressing process conditions. After pressing, remove the pressure-sensitive paper and observe the uniformity of the color development area. If the color development is uniform, without color difference spots, and without obvious edge effects, it is judged as "pass"; if there are local spots that are too dark or too light, it is judged as "fail".

[0050] The buffer material, ACF, and glass substrate are hot-pressed according to the ACF bonding process. After cooling, the buffer material is manually peeled off, and the surface of the buffer material and the pressure head is observed for ACF residue, foreign matter, or white spots. If there is no residue or stickiness, it is judged as "qualified"; if there is residue or stickiness, it is judged as "unqualified".

[0051] Table 1 Performance test results of cushioning materials

[0052] The S-PI / SR-1, S-PI / SR-2 and S-PI / SR-3 (Examples 4-6) prepared by this invention are significantly superior to commercially available hot-press silicone sheets (manufactured by Shin-Etsu Chemical Industry Co., Ltd., Japan, HC-20A, 0.2mm) in terms of pressing life, thermal conductivity and antistatic properties, and can meet the requirements of ACF adhesion pressing for cushioning materials.

[0053] In terms of compression life, S-PI / SR-1, S-PI / SR-2 and S-PI / SR-3 all achieved a compression life of 1800 cycles, which is far superior to the 200 cycles of commercially available hot-pressed silicone rubber sheets and the 400 cycles of S-SR. This indicates that the one-step in-situ imidization process combined with the PI fiber skeleton reinforcement structure adopted in this invention can significantly improve the fatigue resistance of the cushioning material and effectively solve the technical problem that existing hot-pressed silicone rubber sheets are prone to cracking, chipping and breakage after multiple high temperature and high pressure cycles.

[0054] In terms of thermal conductivity, the thermal conductivity of S-PI / SR-1, S-PI / SR-2 and S-PI / SR-3 are all higher than that of commercially available hot-pressed silicone rubber sheets (0.70 W / m·K), indicating that the present invention effectively improves the thermal conductivity of the material by adding modified boron nitride (BN) as a thermally conductive filler, which can meet the process requirements of rapid and uniform heat transfer during ACF pressing.

[0055] In terms of antistatic properties, the volume resistivity of S-PI / SR-1, S-PI / SR-2, and S-PI / SR-3 is all 5 × 10⁻⁶. 8 Ω·cm, reaching the antistatic level (10 6 ~10 9The volume resistivity of commercially available thermoplastic silicone rubber sheets is 7 × 10 Ω·cm, while the requirement is Ω·cm. 10 The electrostatic discharge (ESD) is measured in Ω·cm, which is considered insulating. The buffer material prepared by this invention exhibits excellent antistatic properties, effectively preventing damage to the IC chip caused by static electricity buildup during the ACF pressing and peeling process.

[0056] In terms of hardness, the hardness of S-PI / SR-1, S-PI / SR-2, and S-PI / SR-3 is basically the same as that of commercially available hot-pressed silicone sheets, meeting the mechanical performance requirements of the ACF pressing process for the cushioning material. Furthermore, S-PI / SR-1, S-PI / SR-2, and S-PI / SR-3 all passed the pressure-sensitive paper uniformity and release properties tests, indicating that the cushioning material prepared by this invention can achieve uniform pressure transmission and has good ACF release properties.

[0057] This invention employs a periodic verification method, with a 28-day cycle, to compare the changes in the foreign matter defect rate of OLBBonding before and after the introduction of S-PI / SR-1.

[0058] After using the S-PI / SR-1 prepared according to the present invention, the total foreign matter defect rate in the OLB Bonding process significantly decreased from 0.07% to 0.04%. Figure 1 The defect rate of black flaky foreign matter decreased from 0.03% to 0. Figure 2 The above results demonstrate that the present invention can effectively suppress crack initiation and debris shedding of the buffer material during repeated hot-pressing cycles, thereby significantly improving the cleanliness and product yield of the ACF bonding and pressing process.

[0059] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art through related deductions and substitutions based on the inventive concept, without inventive effort, are within the scope of protection of the present invention.

Claims

1. A cushioning material for ACF attachment press bonding, characterized by, The buffer material has a three-layer structure, consisting of polyimide / silicone rubber composite material, silicone rubber, and polyimide / silicone rubber composite material from top to bottom. The polyimide / silicone rubber composite material uses a polyimide fiber skeleton as a reinforcing structure, and silicone rubber fills and coats the polyimide nanofiber skeleton to form an interpenetrating network structure. The silicone rubber is a hot-pressed silicone rubber, and its upper and lower surfaces are tightly bonded to a polyimide / silicone rubber composite material, respectively.

2. The cushioning material for ACF attachment pressing according to claim 1, wherein The thickness of the polyimide / silicone rubber composite material is 0.05~0.1mm; The thickness of the silicone rubber is 0.2~0.25mm.

3. A method of producing the cushioning material for ACF attachment pressing according to claim 1, characterized by, include: The buffer material is obtained by sequentially stacking polyimide / silicone rubber composite material, silicone rubber, and polyimide / silicone rubber composite material, followed by vacuum hot pressing. The vacuum hot pressing process is performed at a temperature of 150~180℃ for 20~30 minutes.

4. The production method according to claim 3, characterized by, The preparation of the polyimide / silicone rubber composite material includes: preparing a polyamic acid nanofiber membrane by electrospinning; mixing and dispersing methylated fumed silica, modified boron nitride, and fluorosilicone to obtain a first mixture; dispersing a platinum catalyst in fluorosilicone to obtain a second mixture; mixing the first mixture and the second mixture evenly, then adding dimethylacetamide for dilution to obtain a silicone rubber infiltration solution; immersing the polyamic acid nanofiber membrane in the silicone rubber infiltration solution, performing vacuum infiltration treatment, and then performing gradient heating treatment to obtain the polyimide / silicone rubber composite material.

5. The preparation method according to claim 4, characterized in that, The electrospinning process conditions are: voltage 15~20kV, receiving distance 10~15cm, spinning rate 0.5~1mL / h, and spinning time 1~2h. The solid content of polyamic acid in the spinning solution used for electrospinning is 12%~15%.

6. The preparation method according to claim 4, characterized in that, The first mixture comprises, by mass parts: 600-800 parts methylated fumed silica, 200-400 parts modified boron nitride, and 9400-11400 parts fluorosilicone. The second mixture comprises: 7-10 parts platinum catalyst and 80-100 parts fluorosilicone; The platinum catalyst is a 2% Karstedt catalyst.

7. The preparation method according to claim 4, characterized in that, The method for preparing the modified boron nitride includes: surface modification treatment of boron nitride using a silane coupling agent; The method for preparing methylated fumed silica includes: surface modification treatment of fumed silica using a methylating agent.

8. The preparation method according to claim 4, characterized in that, The vacuum permeation treatment time is 30~60 minutes.

9. The preparation method according to claim 4, characterized in that, The gradient heating process includes: under nitrogen protection, heating at 2~3℃ / min to 50~80℃ and holding for 0.5~1h, heating at 2~3℃ / min to 100~120℃ and holding for 0.5~1h, heating at 1.5~2℃ / min to 150~180℃ and holding for 1~2h, and heating at 1~1.5℃ / min to 300~350℃ and holding for 1~2h.

10. The application of the cushioning material for ACF bonding as described in any one of claims 1 to 2 in connecting flexible circuit boards and printed circuit boards, glass substrates and driver chips, or thin-film flip-chip packages.

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