Bottom filling glue capable of controlling glue width, preparation method thereof and flip chip

Abstract

The invention provides an underfill adhesive capable of controlling adhesive width, a preparation method of the underfill adhesive and a flip chip, and the underfill adhesive comprises the following components in percentage by mass: 60%-67% of an inorganic filler, 17%-21% of epoxy resin, 15%-20% of an amine curing agent, 0.05%-0.3% of hydrophobic modified fumed silica, 0.1%-0.3% of an amine accelerator and 0.1%-0.2% of carbon black. According to the invention, through a specific formula proportion and control of the addition amount of the hydrophobic modified fumed silica, the control of the hydrophobic degree of the bottom filling glue solution is realized, so that the control of the glue width in the dispensing process is realized, and the reliability and the manufacturing yield of chip packaging are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor chip packaging, and particularly relates to an underfill adhesive for controlling the dispensing adhesive width, a preparation method thereof, and a flip chip. Background Art

[0002] With the trend of miniaturization and high-density packaging of electronic components, flip chips have been widely used due to their smaller size, narrower pitch, high I / O density and other characteristics. The underfill adhesive is a liquid sealant applied between the chip and the substrate, and after curing, it has properties such as high modulus, suitable coefficient of thermal expansion, low moisture absorption rate, and good adhesion to the chip and the substrate. Usually, an underfill adhesive based on epoxy resin is used, and silica fillers and various additives are added to achieve optimal performance.

[0003] When the underfill adhesive acts on the chip and has too strong wettability to the substrate, the underfill adhesive liquid will diffuse in the opposite direction of the chip during filling, resulting in the overflow of the adhesive liquid. If the degree of adhesive liquid overflow continues to increase, it will diffuse to adjacent chips or other components, resulting in a decrease in packaging reliability.

[0004] Therefore, how to provide an underfill adhesive for controlling the dispensing adhesive width, controlling the wettability of the underfill adhesive to the substrate by controlling the proportion of hydrophobically modified fumed silica, thereby controlling the dispensing adhesive width and the diffusion degree of the underfill adhesive liquid, and improving the chip packaging reliability, is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0005] The purpose of the present invention is to provide an underfill adhesive for controlling the dispensing adhesive width, a preparation method thereof, and a flip chip, so as to solve at least one of the above technical problems.

[0006] To achieve the above purpose, in the first aspect of the present invention, an underfill adhesive for controlling the dispensing adhesive width is provided. The underfill adhesive includes the following components in mass percentage: inorganic filler 60% - 67%, epoxy resin 17% - 21%, amine curing agent 15% - 20%, hydrophobically modified fumed silica 0.05% - 0.3%, amine accelerator 0.1% - 0.3%, carbon black 0.1% - 0.2%.

[0007] In the first aspect, the mass percentage of the inorganic filler is 63%, and the mass percentage of the epoxy resin is 19%.

[0008] In the first aspect, the mass percentage of the amine curing agent is 16% - 18%, the mass percentage of the amine accelerator is 0.2%, and the mass percentage of the carbon black is 0.1%.

[0009] In the first aspect, the hydrophobically modified fumed silica is fumed silica surface-modified with polydimethylsiloxane.

[0010] In the first aspect, the epoxy resin is a trifunctional epoxy resin or a tetrafunctional epoxy resin.

[0011] In the first aspect, the inorganic filler is silica with an average particle size of 0.1 - 3 μm.

[0012] In the first aspect, the amine curing agent includes at least one of diethylenetriamine and triethylenetetramine.

[0013] In the first aspect, the amine accelerator is at least one of tris(dimethylaminopropyl)amine and pentamethyldiethylenetriamine.

[0014] The second aspect of the present invention provides a method for preparing an underfill adhesive for controlling the dispensing adhesive width. The preparation method includes: weighing each component of the raw materials according to the mass percentage of the underfill adhesive for controlling the dispensing adhesive width described in the first aspect and placing them in a stirring cup to obtain a first slurry; stirring the first slurry with a first centrifugal stirrer to obtain a second slurry with uniform mixing. The working parameters of the first centrifugal stirrer include: stirring time is 150 - 220 s, rotation speed is 2600 r / min, and revolution speed is 2000 r / min; transferring the second slurry to a three-roll grinder for dispersion treatment to obtain a third slurry with uniform dispersion. The working parameters of the three-roll grinder include: the feeding gap is 6 - 10 μm, and the discharging gap is 3 - 5 μm; performing vacuum degassing on the third slurry with a second centrifugal stirrer to obtain the underfill adhesive. The working parameters of the second centrifugal stirrer include: stirring time is 90 - 120 s, rotation speed is 2600 r / min, and revolution speed is 2000 r / min.

[0015] The third aspect of the present invention provides a flip chip, which has a packaging structure, and the packaging structure includes a material formed by curing the underfill adhesive for controlling the dispensing adhesive width described in the first aspect.

[0016] Beneficial effects: A bottom filling adhesive for controlling the dispensing adhesive width provided by the present invention comprises the following components in mass percentage: 60% - 67% of inorganic filler, 17% - 21% of epoxy resin, 15% - 20% of amine curing agent, 0.05% - 0.3% of hydrophobically modified fumed silica, 0.1% - 0.3% of amine accelerator, and 0.1% - 0.2% of carbon black. Taking epoxy resin as the matrix material, reacting with the amine curing agent under the action of the amine accelerator to complete the material curing. Meanwhile, the performance of the matrix material is improved by combining the uniformly dispersed inorganic filler, and a hydrophobic layer is formed on the surface of the matrix material through the hydrophobically modified fumed silica, so that the wettability of the prepared bottom filling adhesive liquid to the chip substrate is reduced, thereby narrowing the adhesive width during the dispensing process. And after the adhesive liquid is cured, the phenomenon of adhesive liquid overflow is reduced, realizing the perfect encapsulation of the chip and improving the reliability and yield of chip encapsulation. The present invention realizes the control of the hydrophobic degree of the bottom filling adhesive liquid by a specific formulation ratio and controlling the addition amount of the hydrophobically modified fumed silica, thereby realizing the control of the adhesive width size during the dispensing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present specification or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 It is a schematic flow chart of the preparation method of a bottom filling adhesive for controlling the dispensing adhesive width provided by the present invention; Figure 2 It is an effect diagram of the change in the adhesive width before and after curing of the bottom filling adhesive in Comparative Example 1 of the present invention; Figure 3 It is an effect diagram of the change in the adhesive width before and after curing of the bottom filling adhesive in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following will specifically describe the present invention in combination with the specific embodiments and examples, and the advantages and various effects of the present invention will be presented more clearly therefrom. Those skilled in the art should understand that these specific embodiments and examples are used to illustrate the present invention, rather than to limit the present invention.

[0020] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as having the meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as the general understanding of those skilled in the art to which the present invention belongs. In case of contradiction, this specification shall prevail.

[0021] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchase or by existing methods.

[0022] A bottom filling adhesive for controlling the dispensing bead width provided by the present application, the bottom filling adhesive includes the following components by mass percentage: inorganic filler 60% - 67%, epoxy resin 17% - 21%, amine curing agent 15% - 20%, hydrophobically modified fumed silica 0.05% - 0.3%, amine accelerator 0.1% - 0.3%, carbon black 0.1% - 0.2%.

[0023] Specifically, a bottom filling adhesive for controlling the dispensing bead width provided by the present invention includes the following components by mass percentage: inorganic filler 60% - 67%, epoxy resin 17% - 21%, amine curing agent 15% - 20%, hydrophobically modified fumed silica 0.05% - 0.3%, amine accelerator 0.1% - 0.3%, carbon black 0.1% - 0.2%; using epoxy resin as the matrix material, reacting with the amine curing agent under the action of the amine accelerator to complete the curing of the material, and at the same time combining the uniformly dispersed inorganic filler to improve the performance of the matrix material, and forming a hydrophobic layer on the surface of the matrix material through hydrophobically modified fumed silica, so that the wettability of the prepared bottom filling adhesive liquid to the chip substrate is reduced, thereby reducing the bead width of the adhesive liquid during the dispensing process, and after the adhesive liquid is cured, reducing the phenomenon of adhesive liquid overflow, realizing the perfect encapsulation of the chip, and improving the reliability and yield of chip encapsulation. The present invention controls the hydrophobicity degree of the bottom filling adhesive liquid by a specific formulation ratio and controlling the addition amount of hydrophobically modified fumed silica, thereby realizing the control of the bead width size during the dispensing process.

[0024] In some possible embodiments, the mass percentage of the inorganic filler is 63%, and the mass percentage of the epoxy resin is 19%.

[0025] In some possible embodiments, the mass percentage of the amine curing agent is 16% - 18%, the mass percentage of the amine accelerator is 0.2%, and the mass percentage of the carbon black is 0.1%.

[0026] Specifically, under the same conditions, when the wettability of the underfill adhesive to the substrate is too strong, the dispensing width will become larger, resulting in the phenomenon of adhesive overflow. Moreover, as the temperature rises, during the high-temperature curing process of the adhesive, the viscosity reaches the lowest, causing the adhesive to overflow in the opposite direction of the chip. If the overflow continues to increase, it will spread to the outside of adjacent chips, resulting in the risk of reduced packaging reliability of adjacent chips after dispensing. To avoid the overflow of the underfill adhesive after dispensing and the spread of the overflow to adjacent chips during the curing process, the present application provides the underfill adhesive with the above formula ratio to control the size of the adhesive width during the dispensing process, so that the dispensing adhesive width is not too wide at a substrate temperature of 100°C, and under the curing conditions of 165°C / 2H, the adhesive will not overflow and spread to adjacent chips. The present application reduces the wettability of the underfill adhesive by adding hydrophobically modified fumed silica, narrowing the dispensing adhesive width and the degree of diffusion, thereby achieving the effect of suppressing the overflow of the adhesive and improving the reliability of chip packaging.

[0027] In some possible embodiments, the hydrophobically modified fumed silica is polydimethylsiloxane surface-modified fumed silica.

[0028] In the present application, the wettability of the adhesive is reduced by hydrophobically modified fumed silica, and the wettability of the adhesive is controlled by controlling the addition amount of the hydrophobically modified fumed silica, thereby controlling the dispensing adhesive width and the degree of overflow and diffusion of the adhesive. In a specific embodiment, the hydrophobically modified fumed silica can be the surface-treated product models TS-720, TS-610 or TS-530 purchased from Cabot Corporation; and the hydrophilic modified fumed silica used subsequently is also the product model M5 purchased from Cabot Corporation.

[0029] In some possible embodiments, the epoxy resin is a trifunctional epoxy resin or a tetrafunctional epoxy resin.

[0030] In the present application, the epoxy resin is a trifunctional epoxy resin or a tetrafunctional epoxy resin, and its main structural formula is: (Ⅰ) or (Ⅱ) ; Among them, the structural formula (Ⅰ) can be the product models ELM-100 or ELM-100H of Sumitomo Chemical. ELM-100 and ELM-100H have the same structure but different molecular weights; the structural formula (Ⅱ) can be the product model ELM-434 of Sumitomo Chemical.

[0031] In some possible embodiments, the inorganic filler is silica with an average particle size of 0.1 - 3 μm.

[0032] Inorganic fillers are conventional components of underfill adhesives, mainly used to reduce the thermal expansion coefficient of the system. In this application, silica with an average particle size of 0.1 - 3 μm is selected as the inorganic filler to enhance the strength of the system and enable it to be uniformly dispersed in the epoxy resin.

[0033] In some possible embodiments, the amine curing agent includes at least one of diethylenetriamine and triethylenetetramine.

[0034] In some possible embodiments, the amine accelerator is at least one of tris(dimethylaminopropyl)amine and pentamethyldiethylenetriamine.

[0035] Amine accelerators are used to regulate the curing reaction time. Under the action of amine accelerators, the amine curing agent reacts with the epoxy resin, causing the system to change from a flowing state to a solid state, thereby completing the fixed encapsulation of the chip.

[0036] Based on a general inventive concept, the present application also provides a method for preparing an underfill adhesive for controlling the dispensing bead width, the preparation method comprising: S1. Weigh each component of the raw materials according to the mass percentage of the underfill adhesive for controlling the dispensing bead width described in the first aspect, and place them in a stirring cup to obtain a first slurry; S2. Stir the first slurry by a first centrifugal mixer to obtain a second slurry with uniform mixing; the working parameters of the first centrifugal mixer include: stirring time is 150 - 220 s, rotation speed is 2600 r / min, and revolution speed is 2000 r / min; S3. Transfer the second slurry to a three-roll grinder for dispersion treatment to obtain a third slurry with uniform dispersion; the working parameters of the three-roll grinder include: the feeding gap is 6 - 10 μm, and the discharging gap is 3 - 5 μm; S4. Perform vacuum degassing on the third slurry by a second centrifugal mixer to obtain an underfill adhesive; the working parameters of the second centrifugal mixer include: stirring time is 90 - 120 s, rotation speed is 2600 r / min, and revolution speed is 2000 r / min.

[0037] Specifically, by adjusting the working parameters of the first centrifugal mixer, each component of the raw materials can be fully and uniformly mixed. At the same time, through further mixing by the three-roll grinder, each component in the ground third slurry is under the same conditions, thereby laying a foundation for the subsequent curing reaction. Finally, through vacuum degassing treatment, it is avoided that bubbles are generated during the curing process of the slurry, causing voids and affecting the production yield of chip encapsulation.

[0038] Based on a general inventive concept, the present application further provides a flip chip having a packaging structure, wherein the packaging structure includes a material formed by curing the bottom filling glue for controlling the dispensing glue width as described in the first aspect.

[0039] 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.

[0040] The components of the raw materials in Comparative Examples 1-4 and Examples 1-3 in this application are shown in Table 1 according to mass percentage: Table 1 Distribution ratio of each group of raw materials The performance test of the bottom filling glue provided in Examples 1-3 and Comparative Examples 1-4 was performed, and the specific test process is as follows: 1. Glue width test: Use Musashi smart300 voltage valve dispensing machine, dispensing head 100μm, dispensing pressure 0.14MPa, put bottom filling glue on the glass sheet (glass sheet is treated by plasma cleaning machine, treatment conditions 500W / O2 / 600s), and put the glass sheet on a 100℃ hot plate. After 10min, measure the width of the bottom filling glue by electron microscope, and put the glass sheet at 165℃, and measure the width of the bottom filling glue after curing by electron microscope after 2H; 2. Test method for fluidity: Stick a square glass sheet with a side length of 20 mm and a thickness of 0.5 mm on a glass slide with 30μm thick double-sided tape at the four corners, place it on a 100℃ hot plate, preheat for three minutes, use a fine steel needle to apply the bottom filling glue to be tested horizontally along one edge of the square glass sheet, and start timing at the same time. Under the action of capillary force, the bottom filling glue will flow at the bottom of the glass sheet, and record the time when it is full.

[0041] 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, no hydrophobic modified fumed silica was added. The width of the bottom filling glue prepared became larger after curing. The effect diagram before and after curing is shown in FIG. Figure 2 As shown, the chip packaging requirements cannot be met; (2) In Comparative Example 2, hydrophilic modified fumed silica was added, and the bottom filling glue prepared not only had a large glue width during dispensing, but also had a further increased width after curing, which could not meet the chip packaging requirements; (3) In Comparative Example 3, the addition amount of the hydrophobic modified fumed silica was small and was not sufficient to affect the wettability of the underfill adhesive. The change in the adhesive width before and after the curing of the adhesive liquid was large, and there was still a phenomenon of overflow and diffusion of the adhesive liquid during the chip packaging process. In Comparative Example 4, the addition amount of the hydrophobic modified fumed silica was large. Although it could reduce the adhesive width, it also decreased the dispersion degree of the system, resulting in poor fluidity of the adhesive liquid, inability to fill the gap, and failure to meet the chip packaging requirements. (4) The underfill adhesives prepared according to the specific formulation ratios in Examples 1-3 had good fluidity, and the change in the adhesive width of the adhesive liquid before and after curing was small. The effect diagrams are as Figure 3 shown and met the chip packaging requirements.

[0042] In summary, the underfill prepared by the specific formulation ratio of the present application has excellent fluidity, moderate wettability to the chip substrate, can prevent the reverse flow of the adhesive liquid, and has a small change in the adhesive width before and after curing. At the same time, the size of the adhesive width can be controlled by controlling the addition amount of the hydrophobic modified fumed silica to be suitable for filling gaps of different sizes, complete the chip packaging, and improve the reliability and production yield of the chip packaging.

[0043] Finally, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0044] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0045] 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 equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. An underfill adhesive for controlling the dispensing width of glue, characterized in that, The underfill glue comprises the following components by mass percentage: 60% - 67% of inorganic filler, 17% - 21% of epoxy resin, 15% - 20% of amine curing agent, 0.05% - 0.3% of hydrophobic modified fumed silica, 0.1% - 0.3% of amine accelerator, and 0.1% - 0.2% of carbon black.

2. The underfill adhesive for controlling the dispensing bead width according to claim 1, wherein The mass percentage of the inorganic filler is 63%, and the mass percentage of the epoxy resin is 19%.

3. The underfill glue for controlling the dispensing glue width according to claim 1, wherein The mass percentage of the amine curing agent is 16% - 18%, the mass percentage of the amine accelerator is 0.2%, and the mass percentage of the carbon black is 0.1%.

4. The underfill glue for controlling the dispensing glue width according to any one of claims 1-3, characterized in that, The hydrophobic modified fumed silica is fumed silica surface modified by polydimethylsiloxane.

5. The underfill adhesive for controlling the dispensing bead width according to any one of claims 1-3, characterized in that, The epoxy resin is trifunctional epoxy resin or tetrafunctional epoxy resin.

6. The underfill glue for controlling the dispensing glue width according to any one of claims 1-3, wherein The inorganic filler is silica with an average particle size of 0.1 - 3 μm.

7. The underfill glue for controlling the dispensing glue width according to any one of claims 1-3, characterized in that The amine curing agent includes at least one of diethylenetriamine and triethylenetetramine.

8. The underfill glue for controlling the dispensing glue width according to any one of claims 1-3, characterized in that, The amine accelerator includes at least one of tris(dimethylaminopropyl)amine and pentamethyldiethylenetriamine.

9. A method for preparing an underfill adhesive for controlling the width of the dispensed adhesive, characterized in that, The preparation method includes: Weighing each component of the raw materials according to the mass percentage of the underfill glue for controlling the dispensing glue width as described in any one of claims 1 - 8, and placing them in a stirring cup to obtain a first slurry; Stirring the first slurry by a first centrifugal mixer to obtain a second slurry with uniform mixing; the working parameters of the first centrifugal mixer include: stirring time is 150 - 220 s, rotation speed is 2600 r / min, and revolution speed is 2000 r / min; Transferring the second slurry to a three - roll mill for dispersion treatment to obtain a third slurry with uniform dispersion; the working parameters of the three - roll mill include: feeding gap is 6 - 10 μm, and discharging gap is 3 - 5 μm; Performing vacuum degassing on the third slurry by a second centrifugal mixer to obtain the underfill glue; the working parameters of the second centrifugal mixer include: stirring time is 90 - 120 s, rotation speed is 2600 r / min, and revolution speed is 2000 r / min.

10. A flip chip, characterized in that, The flip - chip has a packaging structure, and the packaging structure includes a material formed by curing the underfill glue for controlling the dispensing glue width as described in any one of claims 1 - 8.

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