A method for preparing nano-silica for electronic potting adhesive filler
By combining stepwise hydrolysis and polycondensation with a rotary ceramic membrane filter, the problem of gel separation was solved, enabling the efficient preparation of nano-silica, meeting the performance requirements of electronic potting compounds, and reducing raw material loss and environmental pollution.
Patent Information
- Application Number
- CN202511040977.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-28
- Publication Date
- 2025-11-21
AI Technical Summary
Existing technologies cannot effectively achieve rapid separation of silica from solvents in gels, resulting in raw material loss, reduced yield, and environmental pollution. There is a lack of industrial solutions for large-scale application.
A stepwise hydrolysis-condensation method combined with a rotary ceramic membrane filter is used to wash and remove impurities from the gel. The gel is formed through hydrolysis-condensation under acidic and alkaline conditions. The microporous structure and rotation of the ceramic membrane are used to achieve efficient separation. An intermittent water replenishment process and a sealing structure are used during the washing process to ensure the reuse of the clean phase and reduce pollution.
It achieves efficient separation of gel materials, reduces raw material loss, increases production, meets the purity and performance requirements of electronic potting compounds for nano-silica fillers, and reduces environmental pollution.
Smart Images
Figure CN120987333A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a method for preparing nano-silica used as filler for electronic encapsulation adhesive. BACKGROUND
[0002] Electronic components (such as chips, capacitors, potentiometers, resistors, etc.) need to be encapsulated with adhesives for the purpose of moisture-proof, shock-proof, heat-proof, friction-proof, insulation, etc. The encapsulation adhesive needs to meet the performance requirements of solidification shrinkage, bonding strength, low impurity content, low dielectric constant, etc. In most epoxy resin type electronic encapsulation adhesives, nano-silica, as a typical disordered mesoporous material, is used as a filler due to its huge internal surface area and uniform pore size, and its mass fraction is as high as 80%.
[0003] There are two methods for preparing nano-silica powder, i.e. the precipitation method and the sol-gel method. Although the precipitation method can produce nano-silica with high purity, good dispersibility and small particle size, it has high energy consumption and cost in the production process.
[0004] The sol-gel method uses silicic acid ester or silicon halide as raw material, alcohol as co-solvent, and acid or alkali solution as catalyst. Through the hydrolysis and polycondensation of silicic acid ester or silicon halide, silica gel is formed. The production process has mild reaction conditions, and the morphology and structure of the material can be controlled in the early stage of synthesis. The reactants can reach a molecular level of uniformity in a short time.
[0005] Although the sol-gel method is more excellent, it has high viscosity of the gel, contains strong corrosive solvents, and many substances are toxic and easy to cause pollution and harm to health. Therefore, the separation of the gel is a common problem in the industry.
[0006] Traditional centrifugation or membrane filtration technology is difficult to adapt to high-viscosity gel systems, not only with low separation efficiency, but also with a certain amount of silica components remaining in the filtrate after separation. This problem not only leads to raw material loss and reduced yield, but also causes environmental pollution due to the emission of residual substances. So far, there is still a lack of industrialized solutions that can be applied on a large scale. SUMMARY
[0007] The purpose of the present application is to provide a method for preparing nano-silica used as filler for electronic encapsulation adhesive, which can effectively solve the problem that the existing technology cannot effectively separate the silica material from the solvent in the gel. The specific solution is as follows:
[0008] A method for preparing nano-silica used as filler for electronic encapsulation adhesive, comprising the following steps:
[0009] S1, hydrolyze and polycondensate part of the silicate or silicon halide, ethanol and part of the water under acidic conditions to form condensed silica;
[0010] S2, water is added to the product obtained in S1, and a basic adjusting agent is added to adjust the pH value to be alkaline, so that the product is further completely hydrolyzed and polycondensed to form a gel product;
[0011] S3, the gel obtained in S2 is washed and impurities are removed by a rotary ceramic membrane filter, and the gel is divided into a concentrated phase and a clear phase, and the clear phase is rectified and reused;
[0012] S4, the concentrated phase washed in S3 is dried and calcined to obtain a silicon dioxide powder.
[0013] Further, in S1, an acidic condition is obtained by adding hydrochloric acid or oxalic acid; in S2, an alkaline environment is obtained by adding ammonia as a basic adjusting agent.
[0014] In order to improve the separation effect and prolong the service life of the separation equipment, the separation assembly in the rotary ceramic membrane filter in S3 is a ceramic membrane sheet, and the surface of the ceramic membrane sheet is provided with micropores.
[0015] The rotary ceramic membrane filter in S3 includes a feed inlet, a clear phase outlet and a concentrated phase outlet, wherein the clear phase outlet is connected to the micropores on the ceramic membrane sheet through a hollow main shaft.
[0016] During separation, the gel material in S2 is injected into the ceramic membrane filter through a pumping system from the feed inlet, and a pressure regulating valve is used to block the outlet of the filter. Under the action of pressure, the clear phase containing dissolved impurities is collected through the micropores on the surface of the ceramic membrane sheet, and the concentrated phase is retained. The rotation of the ceramic membrane sheet driven by the hollow main shaft ensures that the gel material cannot contaminate the micropores on the membrane surface, ensuring that the process in S3 can be operated stably for a long time.
[0017] The rotary ceramic membrane filter is a sealed structure, and the clear phase can be rectified and reused, reducing the emission of toxic and harmful substances and further avoiding environmental pollution caused by solvent evaporation during the filtration and separation process. The hollow main shaft and the micropores on the surface of the ceramic membrane sheet form a closed communication channel, ensuring that the clear phase is in a closed environment during the separation process, minimizing the contact between the solvent and the external air, and preventing pollution from the source.
[0018] Further, the washing process in S3 adopts an intermittent water supplementing process: during the filtration and separation stage, a predetermined amount of washing water is intermittently injected into the filter according to a predetermined period, and the impurities in the concentrated phase are further filtered and removed until no impurities are detected in the composition of the clear phase outlet. At the same time, the remaining concentrated phase is concentrated to a specified volume required by the process, ensuring that the purity of the concentrated phase in the subsequent treatment meets the standard.
[0019] Further, in S4, the drying temperature is 100-120 DEG C, the drying time is 4h; the calcination temperature is 200-300 DEG C, the calcination time is 1h, the membrane area of the rotary ceramic membrane filter is 2m 2, the filtering precision is 5-30nm, the rotating speed is 300-600rpm, and the operating pressure is 0.1-0.15Mpa.
[0020] Further, the water adding amount of S1 and S2 follows scientific proportioning: the water adding amount of S1 under acidic condition is n, which can meet the requirement of alcohol salt partial hydrolysis polycondensation; the water adding amount of S2 under alkaline condition is m, wherein m is set as (3-5)n, and sufficient water amount can provide a good reaction environment for further complete hydrolysis polycondensation of the product, and ensure the integrity and uniformity of the gel formation.
[0021] Beneficial effects:
[0022] The present application adopts the step-by-step hydrolysis polycondensation mode, i.e., first performing partial hydrolysis polycondensation under acidic condition, and then performing complete hydrolysis polycondensation under alkaline condition, which is beneficial to control the reaction progress, and improve the uniformity and purity of the product. Meanwhile, the rotary ceramic membrane filter is used to wash and remove impurities of the gel, and through the unique structure and working mode, the relative movement between the ceramic membrane and the solution to be treated can efficiently remove impurities, and during the filtering process, the gel substance will not adhere to the membrane micro-pores to form a blockage, so that the washing and impurity removal process can be operated stably for a long time, and industrialization can be successfully realized.
[0023] Meanwhile, due to the high filtering precision of the rotary ceramic filter, the effective components in the concentrated phase are greatly reserved, the raw material loss is reduced, and the yield is improved. The prepared nano-silica has low impurity content, and can meet the performance requirement of the electronic potting adhesive on the filler, and can effectively improve the moisture-proof, shock-proof and insulation performance of the electronic potting adhesive. BRIEF DESCRIPTION OF DRAWINGS
[0024] Figure 1 is a flow chart of a method for preparing nano-silica used as a filler of electronic potting adhesive;
[0025] Figure 2 is a clear phase flow diagram of the rotary ceramic membrane filter during the separation process. DETAILED DESCRIPTION
[0026] In order to deepen the understanding of the present application, the present application will be further described in combination with the embodiments and the drawings, and the embodiments are only used to explain the present application, and do not constitute a limitation on the protection scope of the present application.
[0027] Example 1
[0028] Put 20 g of raw material (tetraethyl orthosilicate, TFOS), 80 L of co-solvent (ethanol), 10 mL of catalyst (hydrochloric acid), and 40 L of high-purity water into a reaction kettle, mix thoroughly, and hydrolyze to prepare a standard solvent. After the solvent is left to stand for 24 h, further add 6.5 mL of catalyst ammonia water with a concentration of 0.05 mol / L, mix again, heat for 15 min, and stand for 6.5 h. The viscosity coefficient reaches 0.01-0.015 pa.S, and the solvent forms a gel.
[0029] Put the gel into a rotary ceramic membrane filter with a membrane area of 2 m 2 , a filtration precision of 30 nm, a rotation speed of 400 rpm, and an operating pressure of 0.1 Mpa. The concentrated phase is circulated back to the reaction kettle. As shown in FIG. 1, the clear phase material flows out through the micropores on the ceramic membrane, the hollow spindle, and the clear phase outlet. Figure 2
[0030] The clear phase is removed to a distillation system. During this period, a total of 60 L of washing water is added in batches. When the gel is concentrated to 40 L in the filtration system, no impurities are detected from the clear liquid side, and the washing is complete.
[0031] Put the gel into an oven and dry it at 120°C for 4 h to obtain a silica xerogel. Then, perform calcination treatment on the xerogel at 300°C for 1 h to obtain a silica powder product.
[0032] According to the TG-DSC analysis results, there are no organic groups and residual impurities in the powder. This state is an effect that can be achieved only by calcination at a temperature of 550°C or higher for a conventional silica powder.
[0033] According to IR spectrum analysis, a rich three-dimensional network structure of nanopores is formed inside the powder, which exhibits great activity.
[0034] According to nitrogen adsorption-desorption analysis, the adsorption isotherm of the sample belongs to type IV according to the BDDT classification, which shows perfect mesoporous characteristics.
[0035] Example 2
[0036] Put 40 g of raw material (tetraethyl orthosilicate, TFOS), 160 L of co-solvent (butylene glycol), 20 mL of catalyst (hydrochloric acid), and 80 L of high-purity water into a reaction kettle, mix thoroughly, and hydrolyze to prepare a standard solvent. After the solvent is left to stand for 24 h, further add 15 mL of catalyst ammonia water with a concentration of 0.1 mol / L, mix again, heat for 10 min, and stand for 6 h. The viscosity coefficient reaches 0.01-0.015 pa.S, and the solvent forms a gel.
[0037] Put the gel into a rotary ceramic membrane filter with a membrane area of 2 m 2 , the filter precision 30nm rotary ceramic membrane filter filter, set the speed 400 rpm, operating pressure 0.1 Mpa, the concentration of the circulating back to the reactor, clear phase to distillation system. During the batch total amount of 100L washing water, when the filter system gel to 80L concentration, from the clear side detection no impurities, washing complete.
[0038] The gel into the oven with 120℃ dry 4h get silica xerogel, and then in 200℃ for 1h calcination treatment, get silica powder finished product.
[0039] TG-DSC analysis results, no organic groups and impurities in the powder residue.
[0040] IR spectroscopy analysis, the powder inside the rich nanopore three-dimensional network structure formation, showing a great activity.
[0041] Nitrogen adsorption-desorption analysis, the adsorption isotherm of the sample according to BDDT classification belongs to type IV, showing a perfect mesoporous characteristics.
[0042] Example 3
[0043] 20g raw material (tetraethyl orthosilicate TFOS), 80L eutectic (glycerol and ethanol mixture), 10 mL catalyst (oxalic acid) and 40L high purity water into the reactor, fully stirred and mixed, so that the hydrolysis of standard solvent. Solvent after 24h further addition of concentration of 0.05mol / L catalyst ammonia 6.5 mL, and mixed again heated 10 min 4h, the viscosity coefficient reaches 0.01-0.015 pa.S, the solvent into the gel.
[0044] The gel into the membrane area 2m 2 , the filter precision 5nm rotary ceramic membrane filter filter, set the speed 400 rpm, operating pressure 0.15 Mpa, the concentration of the circulating back to the reactor, clear phase to distillation system. During the batch total amount of 50L washing water, when the filter system gel to 40L concentration, from the clear side detection no impurities, washing complete.
[0045] The gel into the oven with 100℃ dry 4h get silica xerogel, and then in 250℃ for 1h calcination treatment, get silica powder finished product.
[0046] TG-DSC analysis results, no organic groups and impurities in the powder residue.
[0047] IR spectroscopy analysis, the powder inside the rich nanopore three-dimensional network structure formation, showing a great activity.
[0048] The adsorption isotherm of the sample belongs to type IV according to BDDT classification by nitrogen adsorption-desorption analysis, and shows perfect mesoporous characteristics.
[0049] By using the method, the impurity content in the washed gel is low, the subsequent calcination temperature is reduced, and the energy consumption is saved.
[0050] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the present application, and they should be covered in the scope of the claims of the present application.
Claims
1. A method of preparing nanosilica for use in electronic potting compound fillers, characterized by, The application relates to a method for preparing silica powder, comprising the following steps: S1, under acid conditions, a silicate or a silicon halide is partially hydrolyzed and polycondensed with ethanol and part of water to form concentrated silica gel; S2, water is added to the product obtained in S1, and an alkaline adjusting agent is added to adjust the pH value to alkaline, so that the product is further completely hydrolyzed and polycondensed to form a gel product; S3, the gel obtained in S2 is washed and impurities are removed through a rotary ceramic membrane filter, the gel is divided into a concentrated phase and a clear phase, and the clear phase is rectified and reused; S4, the concentrated phase after washing in S3 is dried and calcined to obtain silica powder.
2. The method for preparing nano-silica for electronic potting compound fillers according to claim 1, characterized in that... In S1, the acid condition is obtained by adding hydrochloric acid or oxalic acid; in S2, the alkaline environment is obtained by adding ammonia as the alkaline adjusting agent.
3. The method for preparing nano-silica for electronic potting compound fillers according to claim 1, characterized in that... The separation component in the rotary ceramic membrane filter in S3 is a ceramic membrane sheet, and the surface of the ceramic membrane sheet is provided with micropores. During separation, the clear phase is collected through the micropores on the surface of the ceramic membrane sheet through the relative movement between the ceramic membrane sheet and the solution to be treated, and the concentrated phase is synchronously reserved.
4. The method for preparing nano-silica for electronic potting compound fillers according to claim 3, characterized in that... The rotary ceramic membrane filter in S3 is a sealed structure, and comprises a feeding port, a clear phase discharging port and a concentrated phase discharging port, wherein the clear phase discharging port is connected with the micropores on the ceramic membrane sheet through a hollow pipeline.
5. The method for preparing nano-silica for electronic potting compound fillers according to claim 4, characterized in that... The membrane area of the rotary ceramic membrane filter is 2 m2, the filtering precision is 5-30 nm, the rotating speed is 300-600 rpm, and the operating pressure is 0.1-0.15 Mpa.
6. The method for preparing nano-silica for electronic potting compound fillers according to claim 3, characterized in that... In S3, a certain amount of washing water is intermittently injected during the washing process until no impurities are detected after the discharging detection at the clear phase discharging port, and at this time, the concentrated phase is concentrated to a specified volume.
7. The method for preparing nano-silica for electronic potting compound fillers according to claim 3, characterized in that... In S4, the drying temperature is 100-120 DEG C, the drying time is 4 h, the calcining temperature is 200-300 DEG C, and the calcining time is 1 h.
8. A method for preparing nano-silica for electronic potting compound fillers according to claim 3, characterized in that... In S1, the water amount under the acid condition is n; in S2, the water amount under the alkaline condition is m, wherein m=(3-5)n.