Low-warpage underfill adhesive for FC-BGA (Fiber Channel Ball Grid Array) packaging, preparation method of low-warpage underfill adhesive and flip chip

Abstract

The invention provides a low-warpage underfill adhesive for FC-BGA packaging, a preparation method thereof and a flip chip. The underfill adhesive comprises the following components in percentage by mass: 50%-60% of silicon dioxide, 24%-29% of epoxy resin, 16%-20% of a curing agent, 0.1%-0.2% of carbon black and 0.1%-0.2% of an accelerant. Wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane modified epoxy resin and phenolic aldehyde modified epoxy resin. By adjusting the proportion of the high-purity bisphenol A epoxy resin, the polyurethane modified epoxy resin and the phenolic aldehyde modified epoxy resin and combining the curing agent and the accelerant, the stress of the underfill adhesive is integrally reduced, and the underfill adhesive with good fluidity and low warpage is obtained; therefore, the packaging yield and the packaging efficiency of chip packaging are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chip packaging, and particularly relates to a low-warpage bottom filling adhesive for FC-BGA packaging, a preparation method thereof and a flip chip. Background Art

[0002] FC-BGA (Flip Chip Ball Grid Array) packaging is usually called flip chip ball grid array packaging technology. It is an advanced packaging technology. Its main feature is to directly solder the processor chip on the packaging substrate, eliminating the traditional pin soldering process. FC-BGA packaging has the advantages of high electrical performance, good heat dissipation, high I / O density, low electromagnetic interference, high frequency tolerance, low loss, good chip high-speed operation stability, small size, high reliability, and improved product yield. It is the most common packaging form for graphics acceleration chips and can meet the high-density, high-speed, high-performance, and multi-functional large-scale integrated circuit chip packaging. However, during the filling process of the bottom filler, warping may occur due to the mismatch of the thermal expansion coefficients of the chip and the substrate, which may lead to chip packaging failure. This is mainly caused by two reasons: one is that the flip-chip solder balls cannot be partially connected to the substrate, or bridges occur between adjacent solder balls, resulting in packaging failure or packaging failure; the other is that there is a large stress between the substrate and the chip after packaging. Excessive stress leads to reliability problems such as solder ball cracking and chip cracking.

[0003] Therefore, how to provide a low-warping bottom filling glue, by adjusting the ratio between the three epoxy resins of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic-modified epoxy resin, to reduce the stress of the bottom filling glue, and thus improve the packaging yield of chip packaging, is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0004] The object of the present invention is to provide a low-warpage bottom filling glue for FC-BGA packaging, a preparation method thereof and a flip chip, so as to solve at least one of the above technical problems.

[0005] To achieve the above-mentioned purpose, the first aspect of the present invention provides a low-warpage bottom filling glue for FC-BGA packaging, wherein the bottom filling glue comprises the following components by mass percentage: 50% to 60% silicon dioxide, 24% to 29% epoxy resin, 16% to 20% curing agent, 0.1% to 0.2% carbon black, and 0.1% to 0.2% accelerator; wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic-modified epoxy resin.

[0006] In the first aspect, the mass percentage of the high-purity bisphenol A epoxy resin is 3% to 12%, the mass percentage of the polyurethane-modified epoxy resin is 3% to 12%, and the mass percentage of the phenol-modified epoxy resin is 3% to 12%.

[0007] In the first aspect, the mass percentage of the curing agent is 16.7%, the mass percentage of the carbon black is 0.1%, and the mass percentage of the accelerator is 0.2%.

[0008] In the first aspect, the curing agent is an amine curing agent, and the amine curing agent includes at least one of polyetheramine and diethylenetriamine.

[0009] In the first aspect, the accelerator includes at least one of an amine accelerator and an imidazole accelerator.

[0010] In the first aspect, the amine accelerator includes 2,4,6-tris(dimethylaminomethyl)phenol.

[0011] In the first aspect, the imidazole accelerator includes 1-methylimidazole.

[0012] In the first aspect, the silicon dioxide is spherical silicon dioxide, and the particle size of the spherical silicon dioxide is 0.6 to 3 μm.

[0013] The second aspect of the present invention provides a method for preparing a low-warpage bottom filling glue for FC-BGA packaging as described in the first aspect, the preparation method comprising: accurately weighing each component of the raw material, wherein the components specifically include, by mass percentage: 50% to 60% silicon dioxide, 24% to 29% epoxy resin, 16% to 20% curing agent, 0.1% to 0.2% carbon black, and 0.1% to 0.2% accelerator; wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic-modified epoxy resin; adding the weighed components into a stirring cup, mixing them evenly with a first centrifugal stirrer to obtain a first slurry; transferring the first slurry to a three-roll grinder for dispersion treatment to obtain a uniformly dispersed second slurry; and vacuum degassing the second slurry with a second centrifugal stirrer to obtain a bottom filling glue.

[0014] The third aspect of the present invention provides a flip chip, comprising a substrate, a chip arranged on a surface of the substrate, and a plurality of spaced solder bumps arranged between the substrate and the chip and electrically connected to the substrate and the chip, wherein the gap between the substrate and the chip is filled with a bottom filling material, and the bottom filling material is formed by curing the low warpage bottom filling glue for FC-BGA packaging described in the first aspect.

[0015] Beneficial effects: The invention provides a low-warpage bottom filling glue for FC-BGA packaging, which comprises the following components by mass percentage: 50%-60% silicon dioxide, 24%-29% epoxy resin, 16%-20% curing agent, 0.1%-0.2% carbon black, and 0.1%-0.2% accelerator; wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic modified epoxy resin; the stress in the bottom filling glue is reduced by the high-purity bisphenol A epoxy resin, the elastic modulus of the bottom filling glue is improved by the interpenetrating polymer network structure inside the polyurethane-modified epoxy resin, and more epoxy values ​​are provided by the phenolic modified epoxy resin. When reacting with the curing agent, more reaction cross-linking points can be provided to form a three-dimensional rigid structure with high cross-linking density, thereby improving the thermal stability and glass transition temperature of the bottom filling glue, and at the same time, the reaction rate of the curing cross-linking reaction is improved by the accelerator. The present invention adjusts the ratio of three epoxy resins, namely, high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic-modified epoxy resin, and combines a curing agent and an accelerator to reduce the stress of the bottom filling glue as a whole, thereby obtaining a bottom filling glue with good fluidity and low warpage, thereby improving the packaging yield and packaging efficiency of chip packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 The present invention provides a flow chart of a method for preparing a low-warpage bottom filling adhesive for FC-BGA packaging. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are used to illustrate the present invention, rather than to limit the present invention.

[0019] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0020] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or obtained by existing methods.

[0021] The present invention provides a low-warpage bottom filling glue for FC-BGA packaging, wherein the bottom filling glue comprises the following components by mass percentage: 50% to 60% silicon dioxide, 24% to 29% epoxy resin, 16% to 20% curing agent, 0.1% to 0.2% carbon black, and 0.1% to 0.2% accelerator; wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic-modified epoxy resin.

[0022] Specifically, the present invention provides a low-warpage bottom filling glue for FC-BGA packaging, which includes the following components in mass percentage: 50% to 60% silicon dioxide, 24% to 29% epoxy resin, 16% to 20% curing agent, 0.1% to 0.2% carbon black, and 0.1% to 0.2% accelerator; wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic modified epoxy resin; the stress in the bottom filling glue is reduced by the high-purity bisphenol A epoxy resin, the elastic modulus of the bottom filling glue is improved by the interpenetrating polymer network structure inside the polyurethane-modified epoxy resin, and more epoxy values ​​are provided by the phenolic modified epoxy resin. When reacting with the curing agent, more reaction cross-linking points can be provided to form a three-dimensional rigid structure with a high cross-linking density, thereby improving the thermal stability and glass transition temperature of the bottom filling glue, and at the same time, the reaction rate of the curing cross-linking reaction is improved by the accelerator. The present invention adjusts the ratio of three epoxy resins, namely, high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic-modified epoxy resin, and combines a curing agent and an accelerator to reduce the stress of the bottom filling glue as a whole, thereby obtaining a bottom filling glue with good fluidity and low warpage, thereby improving the packaging yield and packaging efficiency of chip packaging.

[0023] In some possible embodiments, the mass percentage of the high-purity bisphenol A epoxy resin is 3% to 12%, the mass percentage of the polyurethane modified epoxy resin is 3% to 12%, and the mass percentage of the phenolic modified epoxy resin is 3% to 12%.

[0024] This is because the impurities in the polymer are stress concentrators. When the stress balance is destroyed, the bonding part of the product will crack or warp due to stress imbalance. The high-purity bisphenol A epoxy resin can effectively reduce the warping of the bottom filling glue during the cross-linking and curing process because of its low impurities; the polyurethane modified epoxy resin can provide a good elastic modulus for the bottom filling glue because it contains a highly elastic polyurethane structure; the phenolic modified epoxy resin contains an ultra-high epoxy value, which provides more reaction cross-linking points for the curing reaction, which is conducive to the formation of a three-dimensional rigid structure with a high cross-linking density. By adjusting the ratio between the three epoxy resins of high-purity bisphenol A epoxy resin, polyurethane modified epoxy resin and phenolic modified epoxy resin, the warping, fluidity and thermal stability of the bottom filling glue can be controlled to obtain a bottom filling glue with good fluidity, moderate modulus and low warping, so that it has good reliability when encapsulating the chip, thereby improving the packaging yield of the bottom filling glue encapsulated chip. In a specific embodiment, the model of high-purity bisphenol A epoxy resin can be DER330 or DER332, the model of polyurethane modified epoxy resin can be DER791, EPU300A, EPU133L, EPU133S or EPU253, and the model of phenolic modified epoxy resin can be CNE220, N-730A or N-740.

[0025] In some possible embodiments, the mass percentage of the curing agent is 16.7%, the mass percentage of the carbon black is 0.1%, and the mass percentage of the accelerator is 0.2%.

[0026] In some possible embodiments, the curing agent is an amine curing agent, and the amine curing agent includes at least one of polyetheramine and diethylenetriamine.

[0027] Those skilled in the art can understand that when the glue fills the bottom of the chip, the glue and the chip are placed at high temperature, and the amine curing agent reacts with the epoxy resin, so that the two epoxy resins are cross-linked to form a three-dimensional network structure compound to improve the strength of the bottom filling glue. In a specific embodiment, the model of the polyetheramine is D400.

[0028] In some possible embodiments, the accelerator includes at least one of an amine accelerator and an imidazole accelerator.

[0029] In some possible embodiments, the amine accelerator includes 2,4,6-tris(dimethylaminomethyl)phenol.

[0030] In some possible embodiments, the imidazole accelerator includes 1-methylimidazole.

[0031] This is because, in the present application, the accelerator is equivalent to a catalyst, which can promote the cross-linking and curing reaction between the amine curing agent and the epoxy resin to reduce the curing time of the glue and improve the efficiency of chip packaging.

[0032] In some possible embodiments, the silicon dioxide is spherical silicon dioxide, and the particle size of the spherical silicon dioxide is 0.6 to 3 μm.

[0033] Those skilled in the art can understand that selecting spherical silica as a filler can reduce the thermal expansion coefficient and hygroscopicity of the bottom filler and enhance the modulus of the bottom filler; at the same time, controlling the particle size of the spherical silica to 0.6 to 3 μm can improve the dispersibility of the filler in the epoxy resin.

[0034] Based on a general inventive concept, see Figure 1 The second aspect of the present invention provides a method for preparing the low warpage bottom filling glue for FC-BGA packaging as described in the first aspect, the preparation method comprising: S1. Accurately weigh the raw material components, wherein the components include, by mass percentage, 50% to 60% silicon dioxide, 24% to 29% epoxy resin, 16% to 20% curing agent, 0.1% to 0.2% carbon black, and 0.1% to 0.2% accelerator; wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin, and phenolic-modified epoxy resin; S2, adding the weighed components into a stirring cup, and mixing them evenly by a first centrifugal stirrer to obtain a first slurry; wherein the working parameters of the first centrifugal stirrer are set as follows: stirring time is 85 to 170 seconds, rotation is 1250 r / min, and revolution is 1520 r / min; S3, transferring the first slurry to a three-roll mill for dispersion treatment to obtain a uniformly dispersed second slurry; wherein the working parameters of the three-roll mill are set as follows: the feed gap is 10 to 35 μm, and the discharge gap is 5 to 15 μm; S4, vacuum degassing the second slurry by a second centrifugal mixer to obtain a bottom filling glue; wherein the working parameters of the second centrifugal mixer are set as follows: stirring time is 65 to 90 seconds, rotation is 1250 r / min, and revolution is 1520 r / min; Specifically, the present invention provides a method for preparing a low-warpage bottom filling glue for FC-BGA packaging. First, weigh each component of the raw material according to a specific formula ratio; second, add each weighed component into a stirring cup in turn, and stir and mix to obtain a uniform first slurry; then, transfer the uniformly mixed first slurry to a three-roller grinder for dispersion treatment, and adjust the feeding gap and the discharging gap of the three rollers to control the particle size of the second slurry and improve the compatibility between the components of the raw materials; finally, perform vacuum degassing treatment on the dispersed second slurry to remove the gas generated during the mixing process to obtain a bottom filling glue with uniform dispersion and good fluidity. In addition, the bottom filling glue prepared by the preparation method provided by the present invention is used to fill the gap between the chip and the substrate in the flip chip, so that the glue can be evenly distributed between the chip and the substrate, and after curing, it has low warpage and good thermal stability, thereby improving the reliability of the flip chip packaging.

[0035] Based on a general inventive concept, the third aspect of the present invention provides a flip chip, including a substrate, a chip arranged on a surface of the substrate, and a plurality of spaced solder bumps arranged between the substrate and the chip and electrically connected to the substrate and the chip, the gap between the substrate and the chip is filled with a bottom filling material, and the bottom filling material is formed by curing the low warpage bottom filling glue for FC-BGA packaging described in the first aspect.

[0036] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0037] Example 1 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 55%, epoxy resin DER330: 9%, epoxy resin EPU253: 9%, epoxy resin CNE220: 9%, curing agent D400: 16.7%, carbon black: 0.1%, accelerator DMP30: 0.2%; The specific steps of preparing the above bottom filling glue are as follows: (1) Weigh each component according to the mass percentage of each component of the above-mentioned bottom filling glue raw material; (2) Add the weighed components into a stirring cup, set the working parameters of the first centrifugal stirrer to a stirring time of 85 to 170 seconds, a rotation of 1250 r / min, and a revolution of 1520 r / min, and mix them evenly to obtain a first slurry; (3) transferring the first slurry to a three-roll mill for dispersion treatment, setting the working parameters of the three-roll mill to a feed gap of 10 to 35 μm and a discharge gap of 5 to 15 μm, to obtain a uniformly dispersed second slurry; (4) The second slurry is vacuum degassed by a second centrifugal mixer. The working parameters of the second centrifugal mixer are set as a stirring time of 65 to 90 seconds, a rotation of 1250 r / min, and a revolution of 1520 r / min to obtain a bottom filling adhesive with low warpage and good fluidity.

[0038] Example 2 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 55%, epoxy resin DER332: 3%, epoxy resin DER791: 12%, epoxy resin N-740: 12%, curing agent diethylenetriamine: 16.7%, carbon black: 0.1%, accelerator 1-methylimidazole: 0.2%; The preparation method of the bottom filling glue in this embodiment is the same as the preparation method of the bottom filling glue in embodiment 1.

[0039] Example 3 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 55%, epoxy resin DER330: 12%, epoxy resin EPU253: 3%, epoxy resin CNE220: 12%, curing agent diethylenetriamine: 16.7%, carbon black: 0.1%, accelerator DMP30: 0.2%; The preparation method of the bottom filling glue in this embodiment is the same as the preparation method of the bottom filling glue in embodiment 1.

[0040] Example 4 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 55%, epoxy resin DER332: 12%, epoxy resin EPU133L: 12%, epoxy resin N-730A: 3%, curing agent D400: 16.7%, carbon black: 0.1%, accelerator 1-methylimidazole: 0.2%; The preparation method of the bottom filling glue in this embodiment is the same as the preparation method of the bottom filling glue in embodiment 1.

[0041] Comparative Example 1 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 55%, epoxy resin DER330: 13%, epoxy resin CNE220: 13%, curing agent D400: 18.7%, carbon black: 0.1%, accelerator DMP30: 0.2%; The preparation method of the bottom filling glue in this comparative example is the same as the preparation method of the bottom filling glue in Example 1.

[0042] Comparative Example 2 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 55%, epoxy resin DER330: 13%, epoxy resin DER791: 13%, curing agent D400: 18.7%, carbon black: 0.1%, accelerator DMP30: 0.2%; The preparation method of the bottom filling glue in this comparative example is the same as the preparation method of the bottom filling glue in Example 1.

[0043] Comparative Example 3 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 55%, epoxy resin CNE220: 13%, epoxy resin EPU133L: 13%, curing agent D400: 18.7%, carbon black: 0.1%, accelerator DMP30: 0.2%; The preparation method of the bottom filling glue in this comparative example is the same as the preparation method of the bottom filling glue in Example 1.

[0044] Comparative Example 4 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 49%, epoxy resin DER332: 10%, epoxy resin EPU300A: 10%, epoxy resin CNE220: 10%, curing agent diethylenetriamine: 20.7%, carbon black: 0.1%, accelerator 1-methylimidazole: 0.2%; The preparation method of the bottom filling glue in this comparative example is the same as the preparation method of the bottom filling glue in Example 1.

[0045] Comparative Example 5 In terms of mass percentage, the raw materials of the bottom filler include: Filler: 61%, epoxy resin DER330: 7%, epoxy resin EPU133S: 7%, epoxy resin CNE220: 9%, curing agent D400: 15.7%, carbon black: 0.1%, accelerator DMP30: 0.2%; The preparation method of the bottom filling glue in this comparative example is the same as the preparation method of the bottom filling glue in Example 1.

[0046] The bottom filling glues provided in Examples 1-4 and Comparative Examples 1-5 were subjected to flowability tests, storage modulus, glass transition temperature Tg, thermal expansion coefficient, warpage tests, and high and low temperature cycle tests. The specific test process is as follows: 1. Test method for fluidity: Place a 15×25 mm silicon wafer with copper pillars on the PCB and fix it. Place it on a 110°C hot plate and preheat it for one minute. Use a dispenser to dispense (30-35) mg of the bottom filler to be tested along the long side of the silicon wafer. Under the action of capillary force, the bottom filler will flow to the bottom of the silicon wafer. Record the time it takes to fill the entire silicon wafer. 2. Storage modulus: The test method refers to the standard ASTM E2254-2018. Take a sample that is fully cured at 150°C for 2h. The size of the test sample is 55mm×10mm×3mm. The test is performed using a dynamic mechanical analyzer (DMA). The measurement mode is dual cantilever mode, the vibration frequency is 1Hz, the amplitude is 10μm, and the heating rate is 5°C / min. 3. Glass transition temperature (Tg): The test method refers to the standard ASTM E2254-2018, take a sample that is completely cured at 150°C for 2h, and prepare a test sample with a size of 55mm×10mm×3mm. The test is performed using a dynamic mechanical analyzer (DMA), measuring mode: dual cantilever mode, vibration frequency: 1Hz, amplitude: 10μm, and heating rate: 5°C / min; 4. Thermal expansion coefficient: The test method refers to the standard ASTM E831-2019, take a sample that is completely cured at 150°C for 2h, and prepare a test sample with a size of 5mm×5mm×2mm. Use a static thermomechanical analyzer (TMA) to test the thermal expansion coefficient of the sample. TMA parameter settings: preload force: 0.05N, first scan: room temperature ~ 220°C (heating rate 10°C / min) second scan: room temperature ~ 220°C (heating rate 10°C / min), take the curve data of the second heating section; 5. High and low temperature cycle test: After the fluidity test is completed, the sample is placed at -50℃~150℃ for 500 cycles after being completely cured. Then the sample is sliced ​​and polished, and placed under an ultrasonic scanning microscope to observe whether there is any cracking. If there is any cracking, it is recorded as failed; if there is no cracking, it is recorded as passed. 6. Warpage test: The fully cured sample is placed in a heat reflow cycle at room temperature to 260°C for 3 times, and each cycle is maintained at 260°C for 90 seconds. After the cycle is completed, the warpage height of the sample is measured.

[0047] The test results are shown in Table 2 below: Table 2 Test results From the above table, we can see that: (1) In Comparative Example 1, polyurethane-modified epoxy resin was not added, and high-purity bisphenol A epoxy resin and o-cresol epoxy resin were used as the base resin. The glass transition temperature and storage modulus of the prepared bottom filling glue were relatively high. After the high and low temperature cycle test, the bottom filling glue was prone to cracks, and the thermal expansion coefficient was relatively large. After the thermal reflow cycle, the warping became larger; (2) In Comparative Example 2, no phenolic modified epoxy resin was added, and high-purity bisphenol A epoxy resin and polyurethane modified epoxy resin were used as the base resin. The bottom filling glue prepared had great toughness. After high and low temperature cycle tests, the bottom filling glue was prone to cracks, and the thermal expansion coefficient was large. After the thermal reflow cycle, the warping became larger; (3) In Comparative Example 3, high-purity bisphenol A epoxy resin was not added, and polyurethane-modified epoxy resin and o-cresol epoxy resin were used as the base resin. After the high and low temperature cycle test, the bottom filling glue was prone to cracks and had a large thermal expansion coefficient. After the thermal reflow cycle, the warping became larger; (4) Although high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and o-cresol epoxy resin are used as the base resin in Comparative Example 4, the total amount thereof added exceeds the range specified in the present invention. Although the prepared bottom filling glue has excellent fluidity, the warpage becomes larger after the thermal reflow cycle, and cracks are easily generated after the high and low temperature cycle test, thereby affecting the reliability of the flip chip package.

[0048] (5) Although high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and o-cresol epoxy resin are used as the matrix resin in Comparative Example 5, the total amount thereof added is lower than the range specified in the present invention. Although the prepared bottom filling glue has a high glass transition temperature, the fluidity of the glue is poor and it cannot fill the gap between the substrate and the chip, thus affecting the packaging efficiency of the flip chip. (6) In Examples 1-4, high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and o-cresol epoxy resin are used as the base resins, and the components of the raw materials are all within a specific range. The prepared bottom filling glue has good fluidity, no cracks will appear after high and low temperature cycle tests, and the warpage change after the thermal reflow cycle is small, which can achieve the reliability of flip chip packaging.

[0049] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article, or apparatus.

[0050] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0051] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A low warpage bottom filler for FC-BGA packaging, characterized in that: The bottom filling glue includes the following components by mass percentage: 50% to 60% silicon dioxide, 24% to 29% epoxy resin, 16% to 20% curing agent, 0.1% to 0.2% carbon black, and 0.1% to 0.2% accelerator; wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin and phenolic-modified epoxy resin.

2. The low warpage bottom filler for FC-BGA packaging according to claim 1, characterized in that: The mass percentage of the high-purity bisphenol A epoxy resin is 3% to 12%, the mass percentage of the polyurethane modified epoxy resin is 3% to 12%, and the mass percentage of the phenolic modified epoxy resin is 3% to 12%.

3. The low warpage bottom filler for FC-BGA packaging according to claim 1, characterized in that: The mass percentage of the curing agent is 16.7%, the mass percentage of the carbon black is 0.1%, and the mass percentage of the accelerator is 0.2%.

4. The low warpage bottom filler for FC-BGA packaging according to claim 3, characterized in that: The curing agent is an amine curing agent, and the amine curing agent includes at least one of polyetheramine and diethylenetriamine.

5. The low warpage bottom filler for FC-BGA packaging according to claim 3, characterized in that: The accelerator includes at least one of an amine accelerator and an imidazole accelerator.

6. The low warpage bottom filler for FC-BGA packaging according to claim 5, characterized in that: The amine accelerator includes 2,4,6-tris(dimethylaminomethyl)phenol.

7. The low warpage bottom filler for FC-BGA packaging according to claim 5, characterized in that: The imidazole accelerator includes 1-methylimidazole.

8. The low warpage bottom filler for FC-BGA packaging according to claim 1, characterized in that: The silicon dioxide is spherical silicon dioxide, and the particle size of the spherical silicon dioxide is 0.6 to 3 μm.

9. A method for preparing a low warpage bottom filler for FC-BGA packaging according to any one of claims 1 to 8, characterized in that: The preparation method comprises: Accurately weigh the raw material components, which specifically include, by mass percentage, 50% to 60% silicon dioxide, 24% to 29% epoxy resin, 16% to 20% curing agent, 0.1% to 0.2% carbon black, and 0.1% to 0.2% accelerator; wherein the epoxy resin is composed of high-purity bisphenol A epoxy resin, polyurethane-modified epoxy resin, and phenolic-modified epoxy resin; Add the weighed components into a mixing cup, and mix them evenly using a first centrifugal mixer to obtain a first slurry; Transferring the first slurry to a three-roll mill for dispersion treatment to obtain a uniformly dispersed second slurry; The second slurry is vacuum degassed by a second centrifugal mixer to obtain a bottom filling adhesive.

10. A flip chip, comprising a substrate, a chip disposed on a surface of the substrate, and a plurality of solder bumps disposed between the substrate and the chip and electrically connected to the substrate and the chip, wherein the gap between the substrate and the chip is filled with a bottom filling material, characterized in that: The bottom filling material is formed by curing the low warpage bottom filling glue for FC-BGA packaging according to any one of claims 1 to 8.

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