Preparation method of low-viscosity and high-flow surface-modified silicon micropowder for bottom filling glue

Abstract

The present invention relates to a method for preparing low-viscosity, high-flow surface-modified silicon micropowder for use in underfill adhesives, belonging to the technical field of inorganic fillers. The method first involves surface-modifying spherical silicon micropowder using a silane coupling agent, followed by grading to obtain surface-modified spherical silicon micropowder. The silane coupling agent, a functional group protective agent, and the surface-modified spherical silicon micropowder are then mixed in a mixer to obtain a double-layered spherical silicon micropowder comprising an inner chemical coating and an outer physical coating. The outer physical coating imparts good dispersibility to the filler, while the inner chemical coating imparts good compatibility and dispersibility between the filler and the resin. This product exhibits excellent stability and, when used in underfill adhesives, exhibits low viscosity, high flow, and excellent stability.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic fillers and relates to a method for preparing low-viscosity, high-flow surface-modified silicon micropowder for bottom filling glue. Technical Background

[0002] Underfill is an epoxy resin potting material that fills the bottom of CSP and BGA chips through capillary action. After heating and curing, it forms a solid filling layer, reducing stress impact caused by the difference in thermal expansion coefficient between the chip and the substrate, thereby improving the structural strength and reliability of components. As portable electronic products such as mobile phones and computers become thinner, smaller, and more high-performance, IC packaging is also becoming smaller and more concentrated. CSP / BGA is rapidly gaining popularity and application, and the packaging process requirements for CSP / BGA are becoming increasingly stringent, making the role of underfill increasingly important.

[0003] With the continuous development of electronic products, chip packaging features high density and small size. Traditional large-sized silica powders are no longer able to meet the requirements of high-density, narrow-linewidth flip-chip packaging. Consequently, small-sized silica powders are increasingly being used in underfills. However, due to their small particle size and large specific surface area, silica powders inevitably face difficulties in dispersion, high viscosity, and poor fluidity when used in underfills. These problems do not meet the low viscosity and high fluidity requirements of sealing materials for electronic packaging device installation.

[0004] To address these issues, one can choose a low-viscosity resin or add additives to reduce viscosity and improve fluidity. However, changing the resin or adding additives will inevitably affect product performance. Alternatively, surface modification of the filler can improve compatibility and dispersibility with the resin, thereby reducing viscosity and improving fluidity, ultimately enhancing product performance. Therefore, filler modification is a good option, but if the filler modification is ineffective, it can often have the opposite effect.

[0005] Chinese patent publication CN 105623581A discloses coating spherical silica particles with a polymer containing amino or epoxy functional groups, resulting in a lower viscosity when used in underfills. However, this method uses a polymer coating as the outer layer, which generally has high viscosity. The filler easily agglomerates during the modification process, making it difficult to disperse in underfill products and having limited viscosity reduction effects. Furthermore, the degree of polymerization is difficult to control, making industrialization difficult. Chinese patent publication CN 113403014A discloses modifying silica using a silane coupling agent and styrene monomer. Because the surface-modified styrene layer eliminates hydrogen bonds and reduces the interaction between silica particles, the product has strong dispersibility and is easily dispersed in colloids. However, fillers prepared by this method also suffer from the problem of easy agglomeration and difficulty in dispersion. Furthermore, the styrene coating on the filler surface has limited compatibility with epoxy resin, and the degree of polymerization is difficult to control, making industrialization difficult. Japanese patent document JP6329776B2 selects the spherical silica produced by flame fusion method and VMC method to produce spherical silica as raw materials, first uses silane coupling agent and silazane to be modified under wet conditions, adds polymerization inhibitor to prevent coupling agent polycondensation, then adds acid to make the modified spherical silica condense, then washes, dries, depolymerizes, and finally uses N-phenyl-3-aminopropyl trimethoxysilane to carry out surface treatment. The problem existing in this method is that after the wet modification of silica, the hydroxyl group on the silica surface can be consumed, and when using N-phenyl-3-aminopropyl trimethoxysilane to modify, the modifier will not form chemical coating on the filler surface, and the outer layer is basically a physical coating coupling agent, and the physical coating coupling agent encounters water in the air and is hydrolyzed, and the stability of the product is poor. In addition, polymerization inhibitor and acid are added in the production process, and it is necessary to repeatedly clean, and the process is complex, and there is the problem of environmental protection. Summary of the Invention

[0006] In response to the shortcomings of the existing problems, the present invention provides a method for preparing low-viscosity, high-flow surface-modified silicon micropowder for bottom filling glue. The product prepared by this method is easy to disperse when used in bottom filling glue, has low viscosity, good fluidity, and good interface bonding between the filler and the resin. At the same time, the production process is simple, the process is easy to control, the product has good stability, and is suitable for mass production.

[0007] The technical solutions for implementing the present invention are as follows:

[0008] The present invention is a method for preparing low-viscosity and high-flow surface-modified silicon micropowder for bottom filling glue, which is characterized in that the method comprises the following steps:

[0009] (1) Surface treatment of silicon micropowder: adding spherical silicon micropowder to a mixer for modification, adding a modifier for surface modification, the modification temperature is 80°C to 120°C, and grading to obtain modified silicon micropowder with D50 = 0.1-2.0 μm and D100 ≤ 10 μm; the spherical silicon micropowder before modification has D50 = 0.1-2.0 μm, D100 ≤ 10 μm, and pH = 5.5-7.5; the modifier is a silane coupling agent, and the amount of the modifier added is 0.2% to 2.0% of the weight of the filler;

[0010] (2) taking modified silicon micropowder, a modifier and a functional group protecting agent, adding them into a mixer and mixing them to obtain spherical silicon micropowder with a double-layer coating; the modifier is an epoxy silane coupling agent, and the amount of the modifier added is 0.3% to 3.0% by weight of the modified silicon micropowder; the functional group protecting agent is an imine-type silane coupling agent functional group protecting agent, and the amount added is 5% to 50% of the modifier added in this step.

[0011] The method for preparing low-viscosity, high-flow surface-modified silicon micropowder for bottom filling glue described in the present invention has a further preferred technical solution: in step (1), the spherical silicon micropowder before modification has D50 = 0.5-1.5 μm, D100 ≤ 8.0 μm, and pH = 6.0-7.0.

[0012] The method for preparing the low-viscosity, high-flow surface-modified silica powder for bottom filling glue of the present invention has a further preferred technical solution that, in step (1), the amount of the modifier added is 0.3% to 1.0% of the weight of the filler.

[0013] The method for preparing low-viscosity and high-flow surface-modified silicon micropowder for bottom filling glue described in the present invention has a further preferred technical solution that, in step (1), the silane coupling agent is selected from one or more of epoxy silane, anilino silane, mercapto silane, and methacryloxy silane.

[0014] The method for preparing low-viscosity and high-flow surface-modified silicon micropowder for bottom filling glue described in the present invention has a further preferred technical solution that the pH of the modified silicon micropowder obtained by surface modification in step (1) is 5.5-7.5 and the TGA weight loss is 0.1-1.0%.

[0015] The method for preparing low-viscosity, high-flow surface-modified silicon micropowder for bottom filling glue described in the present invention has a further preferred technical solution that, in step (2), the amount of the modifier added is 0.5% to 2.0% by weight of the modified silicon micropowder.

[0016] The method for preparing low-viscosity, high-flow surface-modified silica powder for bottom filling glue described in the present invention has a further preferred technical solution that, in step (2), the amount of functional group protecting agent added is 10% to 20% of the modifier added in this step.

[0017] The method for preparing low-viscosity, high-flow surface-modified silicon micropowder for bottom filler according to the present invention has a further preferred technical solution in which the modifier in step (2) is an epoxy silane coupling agent selected from one or more of the following structural formulas:

[0018]

[0019] Wherein: R is one of ethyl, propyl, and butyl;

[0020] N = 2 to 16;

[0021] X is an epoxy group: Or epoxycyclohexyl:

[0022] The method for preparing the low-viscosity, high-flow surface-modified silicon micropowder for bottom filling glue of the present invention has a further preferred technical solution that, during the mixing in step (2), the temperature of the mixed material is 0 to 60°C.

[0023] The method for preparing low-viscosity and high-flow surface-modified silica powder for bottom filling glue of the present invention has a further preferred technical solution that the pH of the product obtained in step (2) is 6.0-7.0 and the TGA weight loss is 0.5-2.0%.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The product produced by the method of the present invention has an inner layer of a chemically coated silane coupling agent and an outer layer of a physically coated epoxy silane molecule. By controlling process conditions, optimizing the silane coupling agent, and adding a functional group protecting agent, the outer physically coated coupling agent also exhibits good stability, resulting in good product stability. When the product is used in bottom filler, the outer physically coated epoxy silane coupling agent coating can impart good dispersibility to the filler, while the inner chemical coating layer can improve the compatibility and dispersibility of the filler with the resin. When used in bottom filler, the product is easy to disperse, has low viscosity, good fluidity, and good interface bonding between the filler and the resin. Simultaneously, the production process is simple, the process is easy to control, the product is stable, and it is suitable for mass production. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to specific embodiments.

[0027] The test methods for silicon powder D50, D100, pH, TGA weight loss, viscosity, and flow time in the following examples and comparative examples are as follows:

[0028] D50 and D100 tests: tested using Beckman Coulter LS 13 320 laser particle size analyzer (USA);

[0029] TGA weight loss test: Using the German NETZSCH thermogravimetric analyzer TG209F3, under oxygen atmosphere, the weight loss at 35-800℃ was tested at a heating rate of 10℃ / min.

[0030] Viscosity test: 60 g of silica powder and 40 g of epoxy resin were weighed to prepare a resin mixture. After dispersion and degassing, the viscosity of the resin mixture at 60°C was measured using a Brookfield rotary viscometer DVNEXT.

[0031] Flow time test: The time required for 0.5g of the resin mixture after viscosity testing to flow horizontally through a 110℃, 1cm long, 1cm wide, and 50μm thick mold is the flow time.

[0032] Example 1,

[0033] (1) Preheat the mixer modifier to 80°C, add 500g of spherical silica with D50=0.51μm, D100=2.66μm, and pH=6.0 into the mixer modifier, start stirring, and spray 2.0g of epoxy silane coupling agent 3-glycidylpropyltrimethoxysilane. Continue stirring until the material temperature reaches 110°C, and then perform air flow classification to obtain surface-modified spherical silica powder with a TGA weight loss of 0.23% and a pH of 5.7.

[0034] (2) Add 500 g of surface-modified silica microparticles into a ribbon mixer and start stirring. Mix 3.5 g of epoxysilane 3-glycidylpropyltriethoxysilane and 0.35 g of imine-type silane functional group protecting agent X-12-1172ES from Shin-Etsu Chemical, spray them into the mixer, and stir at 100 rpm for 10 minutes to mix. The final material temperature is 38.2°C to obtain double-layer coated spherical silica.

[0035] Example 2

[0036] (1) Preheat the mixing and modifying machine to 90°C, put 800g of spherical silica with D50=1.71μm, D100=8.52μm, and pH=6.2 into the mixing and modifying machine, start stirring, spray add 2.4g of epoxysilane coupling agent 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, continue stirring until the material temperature reaches 110°C, and then perform air flow classification to obtain surface-modified spherical silicon micropowder with a TGA weight loss of 0.16% and a pH of 6.0.

[0037] (2) 800 g of surface-modified silicon micropowder was added to a ribbon mixer and stirred. 4 g of epoxysilane 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane and 0.4 g of silane coupling agent functional group protecting agent KBE-9103P of Shin-Etsu Chemical were mixed and sprayed into the mixer. The mixture was stirred at 100 rpm for 10 min to obtain a double-layer coated spherical silica.

[0038] Example 3

[0039] (1) Preheat the mixing and modifying machine to 80°C, add 400g of spherical silica with D50=0.32μm, D100=0.79μm, and pH=5.8 into the mixing and modifying machine, start stirring, spray add 2.0g of epoxy silane coupling agent 3-glycidylpropyltrimethoxysilane, continue stirring until the material temperature reaches 110°C, and then perform air flow classification to obtain surface-modified spherical silicon micropowder with a TGA weight loss of 0.31% and a pH of 5.6.

[0040] (2) 400 g of surface-modified silicon micropowder was added to a ribbon mixer and stirred. 4.0 g of epoxysilane 3-(2,3-epoxypropoxy)propylmethyldiethoxysilane and 0.5 g of imine-type silane functional group protecting agent KBE-9103P of Shin-Etsu Chemical were mixed and sprayed into the mixer. The mixture was stirred at 100 rpm for 10 minutes. The final material temperature was 40.1 ° C. to obtain double-layer coated spherical silica.

[0041] Example 4

[0042] (1) Preheat the mixer modifier to 90°C, add 500g of spherical silica with D50=0.51μm, D100=2.66μm, and pH=6.0 into the mixer modifier, start stirring, and spray add 2.0g of aniline coupling agent N-phenyl-3-aminopropyltrimethoxysilane. Continue stirring until the material temperature reaches 120°C, and then perform air flow classification to obtain surface-modified spherical silica powder with a TGA weight loss of 0.25% and a pH of 5.9.

[0043] (2) Add 500 g of surface-modified silica microparticles into a ribbon mixer and start stirring. Mix 3.5 g of epoxysilane 3-glycidylpropyltriethoxysilane and 0.35 g of imine-type silane functional group protecting agent X-12-1172ES from Shin-Etsu Chemical, spray them into the mixer, and stir at 100 rpm for 10 minutes to mix. The final material temperature is 37.6°C to obtain double-layer coated spherical silica.

[0044] Example 5

[0045] (1) Preheat the mixer modifier to 80°C, add 500g of spherical silica with D50=0.51μm, D100=2.66μm, and pH=6.0 into the mixer modifier, start stirring, spray add 2.0g of mercapto coupling agent 3-mercaptopropyltrimethoxysilane, continue stirring until the material temperature reaches 100°C, and then perform air flow classification to obtain surface-modified spherical silica powder with a TGA weight loss of 0.19% and a pH of 5.9.

[0046] (2) Add 500 g of surface-modified silica microparticles into a ribbon mixer and start stirring. Mix 3.5 g of epoxysilane 3-glycidylpropyltriethoxysilane and 0.35 g of imine-type silane functional group protecting agent X-12-1172ES from Shin-Etsu Chemical, spray them into the mixer, and stir at 100 rpm for 10 minutes to mix. The final material temperature is 36.1°C to obtain double-layer coated spherical silica.

[0047] Comparative Example 1

[0048] Compared with Example 1, the pH of the raw materials is different in this comparative example. The pH of the raw materials selected in this comparative example is 4.4.

[0049] Comparative Example 2

[0050] Compared with Example 1, this comparative example has the same step (1) but does not contain step (2).

[0051] Comparative Example 3

[0052] Compared with Example 1, this comparative example does not contain step (1).

[0053] Comparative Example 4

[0054] This comparative example is basically the same as Example 1, except that the modifier in step (2) is 3-glycidylpropyltrimethoxysilane.

[0055] Comparative Example 5

[0056] This comparative example is basically the same as Example 1, except that in step (2), no imine-type silane functional group protecting agent X-12-1172ES produced by Shin-Etsu Chemical is added.

[0057] Comparative Example 6

[0058] This comparative example is basically the same as Example 1, except that the mixing equipment in step (2) is a high-speed stirrer, the preheating temperature of the high-speed stirrer is 80°C, and stirring is continued until the material temperature reaches 110°C.

[0059] The powders of the embodiment and the comparative example were tested, and the results are shown in Table 1 below:

[0060] Table 1

[0061] D50,μm D100,μm TGA weight loss, % pH Example 1 0.51 2.66 0.82 6.8 Example 2 1.71 8.52 0.46 7.0 Example 3 0.32 0.79 1.12 6.6 Example 4 0.51 2.66 0.85 6.9 Example 5 0.51 2.66 0.79 6.8 Comparative Example 1 0.51 2.66 0.85 4.9 Comparative Example 2 0.51 2.66 0.23 5.7 Comparative Example 3 0.51 2.66 0.61 6.9 Comparative Example 4 0.51 2.66 0.76 6.6 Comparative Example 5 0.53 4.41 0.81 5.6 Comparative Example 6 0.55 7.62 0.62 5.7

[0062] As can be seen from Table 1 above: As can be seen from Examples 1-5, the pH of the products of the examples are all within the range of 6.0-7.0. Compared with Example 1, the pH of the raw materials is different in Comparative Example 1, and the pH of the final product is also different, indicating that the pH of the raw materials affects the pH of the final product. Compared with Example 2, Comparative Example 1 does not contain step (2), but the TGA weight loss of the product is smaller and the pH is also lower, indicating that the physical mixing in step (2) will increase the TGA weight loss and increase the pH. Compared with Example 1, Comparative Example 3 does not contain step (1), and the TGA weight loss of the product is slightly smaller, indicating that step (1) can improve the TGA weight loss of the product; compared with Example 1, Comparative Example 4 has different types of modifiers in step (2), Example 1 is 3-glycidylpropyltriethoxysilane and Comparative Example 3 is 3-glycidylpropyltrimethoxysilane, and the product indicators are not much different; compared with Example 1, Comparative Example 5 does not add a functional group protecting agent, and the D50 and D100 of the product are slightly increased, and the pH is slightly decreased, indicating that the functional group protecting agent can reduce agglomeration and improve the pH; compared with Example 1, the mixing equipment in step (2) of Comparative Example 6 is a high-speed stirrer, and the material temperature during mixing is 110°C, while the D50 and D100 of the product are slightly increased, the TGA weight loss is reduced, and the pH is decreased, indicating that high mixing temperature will cause agglomeration.

[0063] The raw materials of Example 1, the samples of the examples and the comparative examples were placed for one week and then subjected to viscosity test and flow time test. The results are shown in Table 2 below:

[0064] Table 2

[0065] Viscosity, mp.s Flow time, s Example 1 Raw materials 6800 ＞1200 Example 1 3850 412 Example 2 1820 118 Example 3 5950 960 Example 4 3440 396 Example 5 3990 440 Comparative Example 1 5465 680 Comparative Example 2 6300 996 Comparative Example 3 5830 900 Comparative Example 4 6600 ＞1200 Comparative Example 5 4750 585 Comparative Example 6 12250 ＞1200

[0066] As can be seen in Table 2 above, when comparing the unmodified raw materials of Examples 1 and 1, the viscosity of Example 1 is significantly reduced and the flow time is significantly improved. While Examples 1, 4, and 5 have the same raw material particle size, the viscosity and flow time of the final products are not significantly different. However, Examples 1, 2, and 3 have different raw materials, yet the viscosity and flow time of the final products vary significantly.

[0067] Compared with Example 1, the pH values ​​of Comparative Example 1 are different. The pH value of Comparative Example 1 is lower, but the viscosity of the final product is large and the flow time is long, indicating that the pH value of the raw materials affects the viscosity and flow time of the product. Compared with Example 1, Comparative Example 2 does not contain step (2), but the viscosity is significantly larger and the flow time is longer, indicating that the physical coating in step (2) can significantly improve the viscosity and fluidity. Compared with Example 1, Comparative Example 3 does not contain step (1), and the viscosity is significantly greater and the flow time is longer, indicating that surface modification in step (1) can improve viscosity and fluidity; Compared with Example 1, the type of modifier in step (2) is different in Example 4, that is, 3-glycidylpropyltriethoxysilane in Example 1 and 3-glycidylpropyltrimethoxysilane in Comparative Example 4, and the viscosity of Comparative Example 4 is significantly greater and the flow time is significantly worse, indicating that the type of modifier in step (2) affects viscosity and fluidity; Compared with Example 1, Comparative Example 5 does not add a functional group protecting agent, and the viscosity and fluidity of the product are poor, indicating that the addition of a functional group protecting agent can improve viscosity and fluidity; Compared with Example 1, the mixing equipment in step (2) is a high-speed stirrer, and the material temperature during mixing is 110°C, and the viscosity of the product increases significantly and the fluidity is significantly worse, indicating that the mixing equipment and temperature conditions have a greater impact on the viscosity and fluidity of the product.

[0068] The samples of the embodiment and comparative example were placed for 1 month, 2 months, and 3 months before viscosity test and flow time test. The results are shown in Table 3 below:

[0069] Table 3

[0070]

[0071]

[0072] As can be seen from Table 3 above, the products of Examples 1-5 all have good stability, and the viscosity and flow time are relatively stable after being placed for 3 months, with little increase. Compared with Example 1, the pH of the raw materials of Comparative Example 1 is different. The pH of the raw materials of Comparative Example 1 is lower, and the viscosity of Comparative Example 1 increases significantly after being placed for 2 months, indicating that the pH has a greater impact on the stability of the product. Compared with Example 1, Comparative Example 4 does not add a functional group protecting agent. After being placed for 1 month, the viscosity and flow time of Comparative Example 4 increase significantly, indicating that the functional group protecting agent can improve the stability of the product.

Claims

1. A method for preparing low-viscosity, high-flow surface-modified silica powder for bottom filling glue, characterized in that: The method comprises the following steps: (1) Surface treatment of silicon micropowder: adding spherical silicon micropowder to a mixer for modification, adding modifier I for surface modification, the modification temperature is 80°C to 120°C, and grading to obtain modified silicon micropowder with D50 = 0.1 to 2.0 μm and D100 ≤ 10 μm; the spherical silicon micropowder before modification has D50 = 0.1 to 2.0 μm, D100 ≤ 10 μm, and pH = 5.5 to 7.5; the modifier I is a silane coupling agent, and the amount of the modifier I added is 0.2% to 2.0% of the weight of the filler; the silane coupling agent is selected from one or more of epoxy silane, anilino silane, mercapto silane, and methacryloxy silane; (2) taking modified silicon micropowder, modifier II and functional group protecting agent and adding them into a mixer for mixing to obtain spherical silicon micropowder with double coating; the modifier II is an epoxy silane coupling agent, and the addition amount of the modifier II is 0.3% to 3.0% of the weight of the modified silicon micropowder; the functional group protecting agent is an imine type silane coupling agent, and the addition amount is 5% to 50% of the modifier II added in this step; the epoxy silane coupling agent is selected from one or more of the following structural formulas: ； Wherein: R is one of ethyl, propyl, and butyl; N=2 to 16; X is an epoxy group: or epoxycyclohexyl .

2. The method for preparing low-viscosity and high-flow surface-modified silicon powder for bottom filler according to claim 1, characterized in that: In step (1), the spherical silicon powder before modification has a D50 of 0.5 to 1.5 μm, a D100 of ≤ 8 μm, and a pH of 6.0 to 7.

0.

3. The method for preparing low-viscosity and high-flow surface-modified silicon powder for bottom filler according to claim 1, characterized in that: In step (1), the amount of modifier I added is 0.3% to 1.0% of the weight of the filler.

4. The method for preparing low-viscosity and high-flow surface-modified silicon powder for underfill according to claim 1, characterized in that: The pH of the modified silicon micropowder obtained by surface modification in step (1) is 5.5-7.5, and the TGA weight loss is 0.1-1%.

5. The method for preparing low-viscosity and high-flow surface-modified silicon powder for underfill according to claim 1, characterized in that: In step (2), the amount of modifier II added is 0.5% to 2.0% by weight of the modified silicon micropowder.

6. The method for preparing low-viscosity and high-flow surface-modified silicon powder for underfill according to claim 1, characterized in that: In step (2), the amount of the functional group protecting agent added is 10% to 20% of the modifier II added in this step.

7. The method for preparing low-viscosity and high-flow surface-modified silica powder for underfill according to claim 1, characterized in that: During the mixing in step (2), the temperature of the mixed material is 0 to 60°C.

8. The method for preparing low-viscosity and high-flow surface-modified silica powder for underfill according to claim 1, characterized in that: The pH of the product obtained in step (2) is 6.0-7.0, and the TGA weight loss is 0.5-2.0%.

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