Alkali-free borosilicate glass with low expansion coefficient and preparation method thereof

Abstract

The invention discloses alkali-free borosilicate glass with a low expansion coefficient and a preparation method thereof, and belongs to the technical field of glass. The alkali-free borosilicate glass with the low expansion coefficient is prepared from the following components in percentage by mass: 40 to 70 percent of SiO2, 10 to 20 percent of Al2O3, 5 to 31 percent of B2O3, 0 to 3 percent of MgO, 0 to 7 percent of CaO, 0 to 2.5 percent of SrO, 0 to 1 percent of BaO, 0 to 0.25 percent of K2O, 0 to 0.25 percent of Li2O and 0 to 0.21 percent of SnO2. The content of SiO2, B2O3 and Al2O3 is 85%-91%, the content of MgO, CaO and BaO is 5%-12%, and the content of Li2O and K2O is 0-0.25%. The glass is low in thermal expansion coefficient, high in chemical stability and suitable for melting. The preparation method is simple and convenient, is suitable for industrial production, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of glass technology, and specifically to a low-expansion-coefficient alkali-free borosilicate glass and its preparation method. Background Technology

[0002] With the continued advancement of artificial intelligence, 5G communication technology, and the miniaturization trend of electronic devices, higher demands are being placed on chip packaging technology. Traditional two-dimensional packaging methods, due to issues such as long interconnect lengths and significant signal transmission delays, are unable to support the transmission requirements of high-frequency and high-speed signals and are gradually becoming inadequate for the development of modern information technology. Against this backdrop, "3D packaging technology" has become an important development direction in the field of advanced packaging. This technology not only provides more robust physical protection for chips but also significantly improves integration without increasing the planar footprint, significantly shortens interconnect distances, and reduces signal transmission losses, thereby comprehensively improving the overall performance of the chip.

[0003] Glass, as a key material in 3D packaging, plays an irreplaceable role in core components such as interposers and substrates. It possesses a tunable low coefficient of thermal expansion, excellent electrical insulation properties, high mechanical strength, good flatness, and stable chemical properties. The low coefficient of thermal expansion allows for good matching with silicon materials, effectively reducing stress and deformation during thermal cycling, preventing warping or cracking of the packaging structure, and significantly improving packaging reliability and lifespan. Simultaneously, glass's excellent insulation properties help reduce signal loss and crosstalk during transmission, supporting signal integrity at higher frequencies. Furthermore, its high mechanical strength and high flatness provide a solid foundation for achieving high-density interconnects and precise interlayer alignment, meeting the stringent requirements of 3D integration for process precision.

[0004] Currently, although organic substrates have advantages such as being lightweight, supporting complex circuit designs, having simple manufacturing processes, and being relatively low in cost, their high-temperature stability is poor, and they are prone to deformation in high-temperature environments, limiting their application in certain high-performance scenarios. Ceramic substrates, on the other hand, exhibit stable dielectric properties and good mechanical strength, which can meet the reliability requirements of integrated circuits, but their manufacturing cost is high and their density is high, making them difficult to adapt to applications with high lightweight requirements.

[0005] Furthermore, the process of creating through-glass vias (TGV) on glass substrates involves etching, sputtering, drilling, and other steps to form the circuit structure. Some of these processes require operation at high temperatures of 500–600 °C. During these high-temperature treatments, alkali metal oxides contained in the glass may diffuse and migrate into adjacent semiconductor materials, causing semiconductor "poisoning" and severely impacting device performance and reliability.

[0006] In this field, alkali-free typically refers to aluminoborosilicate glass with an alkali metal oxide (R2O) content of less than 0.8 wt.%. To reduce the adverse effects of alkali metal oxides and optimize the coefficient of thermal expansion, for example, Chinese invention patent CN101092280A discloses a high elastic modulus aluminoborosilicate glass and its applications, prepared from the following raw materials in weight percentages: 55%~63.5% SiO2, 8%~10.5% B2O3, 15%~21% Al2O3, 0~3.5% MgO, 4%~10% CaO, 0~5% SrO, 1%~5.5% BaO, 0.001%~4% Y2O3, 0~2.5% La2O3, 0~0.5% ZnO, 0~0.3% ZrO2, and 0.005%~0.08% R2O (R = Li, Na, K). This aluminoborosilicate glass has the advantages of a high strain point, low coefficient of thermal expansion, high elastic modulus, and is essentially alkali-free. For example, Chinese invention patent CN102306715A provides an OLEDoS microdisplay device with the following weight percentage composition: 58%~64% SiO2, 8%~15% B2O3, 12%~16% Al2O3, 5%~9% MgO, 6%~8% CaO, 2%~4% BaO, 1%~4% Y2O3, 0%~2% SnO2, 0~0.5% CeO2, 0~1% Cl, and 0.005%~0.1% R2O. The glass plate of this invention is an aluminoborosilicate glass with a high elastic modulus, high strain point, low coefficient of expansion, high elastic modulus, and is essentially alkali-free. However, the complex composition involved in the above technical solutions and the multi-component glass composition impose more restrictions on control in industrial production, which is not conducive to production cost and process optimization.

[0007] In summary, this paper provides a low-expansion-coefficient alkali-free borosilicate glass and its preparation method, which meets the performance indicators such as low expansion coefficient and optimizes the composition and process steps, and is of great significance to related application fields. Summary of the Invention

[0008] In view of the above-mentioned deficiencies of the prior art, in a first aspect of the present invention, a low coefficient of thermal expansion alkali-free borosilicate glass is provided, comprising, by weight percentage, the following components: SiO240%~70%, Al2O310%~20%, B2O35%~31%, MgO 0~3%, CaO 0~7%, SrO 0~2.5%, BaO 0~1%, K2O 0~0.25%, Li2O 0~0.25%, SnO20~0.21%; The sum of the mass percentages of the above components is 100%; among them, the sum of the mass percentages of SiO2+B2O3+Al2O3 is 85%~91%, the sum of the mass percentages of MgO+CaO+BaO is 9%~12%, and the sum of the mass percentages of Li2O+K2O is 0~0.25%.

[0009] Preferably, the low coefficient of thermal expansion alkali-free borosilicate glass comprises, by mass percentage, the following components: SiO251%~65%, Al2O314.5%~19%, B2O310%~22%, MgO 0~3%, CaO 2.3~6.4%, SrO 0~2.5%, BaO 0~1%, K2O 0~0.25%, Li2O 0~0.25%, SnO20~0.21%; The sum of the mass percentages of the above components is 100%; among them, the sum of the mass percentages of SiO2+B2O3+Al2O3 is 86%~90%, the sum of the mass percentages of MgO+CaO+BaO is 9.5%~10.75%, and the sum of the mass percentages of Li2O+K2O is 0~0.25%.

[0010] Preferably, the low coefficient of thermal expansion alkali-free borosilicate glass comprises, by mass percentage, the following components: SiO259%~63%, Al2O317.5~19%, B2O310~14.5%, MgO 0~3%, CaO 2.3~6.4%, SrO 0~2.5%, BaO 0~1%, K2O 0~0.25%, Li2O 0~0.25%, SnO20~0.21%; The sum of the mass percentages of the above components is 100%; among them, the sum of the mass percentages of SiO2+B2O3+Al2O3 is 85%~91%, the sum of the mass percentages of MgO+CaO+BaO is 9%~12%, and the sum of the mass percentages of Li2O+K2O is 0~0.25%.

[0011] The components of the low-expansion-coefficient alkali-free borosilicate glass are sourced from various sources, including: SiO2 from quartz sand; Al2O3 from Al2O3 or Al(OH)3; B2O3 from boric acid; MgO from MgO; BaO from Ba(NO3)2 or BaCO3; CaO from CaSO4, CaCO3, or CaF2; and SrO from Sr(NO3)2 or SrCl2. One or more of the following components—sulfate, nitrate, CaF2, and SnO2—can function as clarifying agents.

[0012] In a second aspect of the present invention, a method for preparing alkali-free borosilicate glass with a low coefficient of thermal expansion according to the first aspect of the present invention is provided, comprising the following steps: (1) Mixing: Weigh all the raw materials according to the formula ratio, and then pour the raw materials into the mixer to mix them to obtain glass raw materials; (2) Melting: Add the glass raw material to the crucible, heat it to a certain temperature to melt it, then cool it down and stir it. After stirring, take out the stirrer and keep it warm for a certain time.

[0013] (3) Molding: After the heat preservation and settling period, pour the molten glass into the hot mold; (4) Annealing: Finally, fine annealing is performed to eliminate stress and obtain low expansion coefficient alkali-free borosilicate glass.

[0014] Preferably, in step (1), the mixing time is 0.5~1.5 h.

[0015] Preferably, in step (2), the temperature is increased to 1550-1600℃ at a rate of 2-5℃ / min and then kept at that temperature for 5-10 hours.

[0016] Preferably, in step (2), the temperature is lowered to 1150~1300 ℃ and stirred for 4~9 h.

[0017] Preferably, in step (2), the temperature is kept stable for 0.5 to 2 hours.

[0018] Preferably, in step (3), the mold temperature is 650~750 ℃.

[0019] Preferably, in step (4), fine annealing is performed at 2~4 ℃ / h.

[0020] Based on the above technical solutions, and considering performance and production, the design concept and principle of this invention are as follows: SiO2 is the main oxide that forms glass, primarily constituting the glass framework with a silicon-oxygen tetrahedral structure. It can reduce the glass's coefficient of thermal expansion and density, and increase its strain point. However, too low a content will reduce the glass's chemical stability, such as its acid resistance. Too high a content makes the glass difficult to melt and easily leads to quartz (cristobalite) defects.

[0021] Al₂O₃ forms either [Al₆] octahedrons or [Al₄] tetrahedrons depending on the oxygen content in the glass. The [Al₄] tetrahedrons act as a mesh, increasing glass stability, reducing the coefficient of thermal expansion, and decreasing glass density. They also raise the strain point and elastic modulus of the glass, increasing its chemical stability. The content of silicon dioxide and aluminum oxide is interdependent; their combined content should be greater than 70% of the total raw material content. This can reduce the molten viscosity of the glass without increasing the coefficient of thermal expansion.

[0022] B2O3 is a secondary component of the network structure in this glass. B2O3 can form triangular and tetrahedral structures in the glass network structure, which can play a good fluxing role.

[0023] BaO helps to lower the dielectric constant, reduce signal transmission loss, balance the charge in the glass network, enhance structural uniformity, and improve resistance to crystallization. When working synergistically with magnesium oxide, BaO can further regulate the coefficient of thermal expansion and optimize the durability and mechanical strength of the glass without significantly increasing viscosity.

[0024] MgO can adjust the coefficient of thermal expansion, reducing the coefficient of thermal expansion to better match silicon-based materials. It can also improve the chemical stability and mechanical strength of glass, adjust the melting temperature and viscosity, and improve processing performance.

[0025] SrO does not increase density, raise the coefficient of linear expansion, or lower the strain point; it also improves solubility. However, excessive content can lead to deterioration of devitrification properties, reduced resistance to acids and alkalis, and decreased durability of anti-corrosion film stripping solutions.

[0026] SnO2 and other materials are raw materials used as clarifiers to replace toxic arsenic oxide. Clarifiers include one or more of sulfates, nitrates, CaF2 and SnO2. Introducing CaF2 and SnO2 as clarifiers can effectively reduce boron glow, promote glass clarification and homogenization, and is environmentally friendly.

[0027] Compared to the composition design in this application, existing technologies include more types of components, such as Y₂O₃, ZrO₂, CeO₂, Cl, La₂O₃, and As₂O₃. Y₂O₃ is commonly used for improving the chemical stability and high-temperature resistance of glass; however, when the Y₂O₃ content is inappropriate, its metal ions act as network modifiers, making the glass's network structure loose and hindering the reduction of its coefficient of thermal expansion. Furthermore, Y₂O₃ has a high melting point and density, which, as a glass component, will increase the melting temperature and the weight of the finished product, and improper handling during cooling can lead to liquid-phase separation. In alkali-free glass, ZrO₂ helps reduce boron volatilization at high temperatures, improving the glass's chemical stability and reducing its coefficient of thermal expansion. However, ZrO₂ also has a high melting point and density, making it difficult to melt; and improper process control of Zr element crystallization nucleation can lead to crystal points in the glass, affecting optical properties. CeO₂ can be used as a highly efficient clarifying agent, but it is more expensive than traditional clarifying agents, and Ce… 4+Strong absorption in the ultraviolet region, extending its absorption edge into the blue-violet region of visible light, causes the glass to exhibit an undesirable yellow tint. Cl, often introduced as a clarifying agent, similarly disrupts the continuity of the silicon-oxygen network, making the glass structure porous and reactive, which is detrimental to optimizing chemical stability. La₂O₃, similar to Y₂O₃, improves the chemical stability and high-temperature resistance of glass; however, La₂O₃ has a high melting temperature and cost, and its poor migration ability during cooling makes it prone to phase separation. The introduction of these components places higher demands on the manufacturing process, energy consumption, and cost. Improper control can affect the optical uniformity and light transmittance of the glass, making it difficult to meet the specifications of encapsulation materials.

[0028] Based on the above concepts and mechanisms, this application designs and re-optimizes the raw material composition of alkali-free borosilicate glass, thereby providing products with advantages such as low coefficient of thermal expansion, high chemical stability, and suitable melting and forming temperatures.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention provides a low coefficient of thermal expansion alkali-free borosilicate glass, as presented in one or more embodiments of this application, wherein the coefficient of thermal expansion of this alkali-free borosilicate glass is 30~38*10 in the temperature range of 20~300℃. -7 / ℃; elastic modulus is 64~76 GPa; dielectric constant at 1 GHz is 4.38~5.66 F / m, dielectric loss is 1.961~4.801*10 -3 At 5 GHz, the dielectric constant is 4.35~5.59 F / m, and the dielectric loss is 3.182~5.48*10. -3 The refractive index is 1.5018~1.5514; the glass density is less than 2.42 g / cm³. 3 The Kirchhoff hardness is higher than 393 kgf / m. 2 All exhibit water resistance grade 1 and acid resistance grade higher than 2. These performance indicators demonstrate that the low-expansion-coefficient alkali-free borosilicate glass of this invention possesses excellent overall performance.

[0030] This invention provides a method for preparing alkali-free borosilicate glass with a low coefficient of thermal expansion. The process is simple, suitable for industrial production, and has broad application prospects. Detailed Implementation

[0031] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0032] In the following embodiments, the low-expansion-coefficient alkali-free borosilicate glass is prepared using the following steps: (1) Mixing: Weigh various raw materials according to the formula ratio designed in each embodiment, and then pour the raw materials into the mixer and mix for 0.5~1.5 h to obtain glass raw material; (2) Melting: Add the glass raw material to the platinum crucible, first heat it to 1550~1600℃ at 2℃ / min to melt it, keep it at the temperature for 5 h, then cool it down and stir for 4 h, the temperature drops to 1150℃~1300℃, after stirring, take out the stirrer and keep it at the temperature for 0.5 h. (3) Molding: After the heat preservation and settling period, the molten glass is poured into a hot mold with a mold temperature of 650~750 ℃; (4) Annealing: Finally, a fine annealing treatment of 4℃ / h is performed to eliminate stress and obtain the corresponding low expansion coefficient alkali-free borosilicate glass.

[0033] In actual preparation, due to the purity of raw materials and the inherent error of equipment, the actual total mass percentage may fluctuate within an acceptable range around the theoretical value (100%), which can also be regarded as being prepared according to the theoretical value.

[0034] The main equipment, operating tools, and testing and characterization methods involved in the embodiments are as follows: (1) Glass melting is carried out using a single crucible melting furnace, with a maximum temperature of 1700 °C; (2) The thermal expansion coefficient of glass between 20 and 300 °C was tested using a NERZSCH DIL 402 Expedis Supreme high and low temperature expansion coefficient tester. The temperature test range of the tester is -150 to 1600 °C. (3) Use a GrindoSonic MK7 elastic modulus tester to test the elastic modulus, shear modulus and Poisson's ratio of the glass; (4) The spectral transmittance of the glass sample was tested using a Lambda 1050 UV / Vis / NIR spectrophotometer manufactured by PerkinElmer. The spectral test range was 250~2500 nm.

[0035] (5) The refractive index of the glass was tested using a Shimadzu GMR-1DT precision goniometer. The temperature coefficient of refractive index test range is -60~160℃. (6) Use Archimedes' water displacement method to test the density of glass.

[0036] Example 1 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 61.60% SiO2, 10.92% B2O3, 16.50% Al2O3, 5.95% CaO, 2.48% SrO, 0.45% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.15%SnO2; The content of SiO2+B2O3+Al2O3 is 89.02%, MgO+CaO+BaO is 10.58%, and Li2O+K2O is 0.25%.

[0037] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 1.

[0038] Table 1: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0039] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0040] Example 2 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 62.10% SiO2, 11.00% B2O3, 17.00% Al2O3, 4.70% CaO, 2.48% SrO, 0.70% BaO, 1.62% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The composition of SiO2+B2O3+Al2O3 is 90.10%, MgO+CaO+BaO is 9.50%, and Li2O+K2O is 0.25%.

[0041] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 2.

[0042] Table 2: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0043] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0044] Example 3 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 61.60% SiO2, 11.37% B2O3, 17.35% Al2O3, 5.20% CaO, 2.46% SrO, 0.00 BaO, 1.70%MgO, 0.00 K2O, 0.25% Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 90.32%, MgO+CaO+BaO are 9.36%, and Li2O+K2O are 0.25%.

[0045] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 3.

[0046] Table 3: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0047] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0048] Example 4 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 61.60% SiO2, 11.37% B2O3, 17.35% Al2O3, 5.20% CaO, 2.46% SrO, 0.00 BaO, 1.70%MgO, 0.00 K2O, 0.25% Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 90.32%, MgO+CaO+BaO are 9.36%, and Li2O+K2O are 0.25%.

[0049] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 4.

[0050] Table 4: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0051] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0052] Example 5 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 69.06% SiO2, 10.74% B2O3, 10.36% Al2O3, 6.03% CaO, 1.06% SrO, 0.00 BaO, 2.48% MgO, 0.00 K2O, 0.15% Li2O, 0.12% SnO2; The percentages of SiO2+B2O3+Al2O3 are 90.16%, MgO+CaO+BaO are 9.57%, and Li2O+K2O are 0.15%.

[0053] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 5.

[0054] Table 5: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0055] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0056] Example 6 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 68.69% SiO2, 10.24% B2O3, 10.11% Al2O3, 6.39% CaO, 1.31% SrO, 0.00 BaO, 2.97%MgO, 0.00 K2O, 0.23% Li2O, 0.06% SnO2; The percentages of SiO2+B2O3+Al2O3 are 89.04%, MgO+CaO+BaO are 10.67%, and Li2O+K2O are 0.23%.

[0057] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 6.

[0058] Table 6: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0059] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0060] Example 7 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 61.43% SiO2, 11.50% B2O3, 16.50% Al2O3, 5.25% CaO, 2.48% SrO, 0.70% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.19% SnO2; The percentages of SiO2+B2O3+Al2O3 are 89.43%, MgO+CaO+BaO are 10.13%, and Li2O+K2O are 0.25%.

[0061] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 7.

[0062] Table 7: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0063] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0064] Example 8 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 61.89% SiO2, 10.50% B2O3, 17.60% Al2O3, 5.13% CaO, 2.40% SrO, 0.50% BaO, 1.52% MgO, 0.25% K2O, 0.00 Li2O, 0.21% SnO2; The composition of SiO2+B2O3+Al2O3 is 89.99%, MgO+CaO+BaO is 9.55%, and Li2O+K2O is 0.25%.

[0065] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 8.

[0066] Table 8: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0067] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0068] Example 9 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 60.26% SiO2, 11.50% B2O3, 17.50% Al2O3, 5.45% CaO, 2.49% SrO, 0.70% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 89.26%, MgO+CaO+BaO are 10.34%, and Li2O+K2O are 0.25%.

[0069] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 9.

[0070] Table 9: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0071] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0072] Example 10 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 60.45% SiO2, 11.50% B2O3, 17.50% Al2O3, 5.25% CaO, 2.50% SrO, 0.70% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The composition of SiO2+B2O3+Al2O3 is 89.45%, MgO+CaO+BaO is 10.15%, and Li2O+K2O is 0.25%.

[0073] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 10.

[0074] Table 10: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0075] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0076] Example 11 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 60.54% SiO2, 11.50% B2O3, 17.50% Al2O3, 5.15% CaO, 2.51% SrO, 0.70% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 89.54%, MgO+CaO+BaO are 10.06%, and Li2O+K2O are 0.25%.

[0077] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 11.

[0078] Table 11: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0079] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0080] Example 12 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 59.73% SiO2, 9.50% B2O3, 17.50% Al2O3, 5.48% CaO, 2.51% SrO, 0.70% BaO, 1.90%MgO, 0.00 K2O, 2.50% Li2O, 0.18% SnO2; The percentages of SiO2+B2O3+Al2O3 were 86.73%, MgO+CaO+BaO were 10.59%, and Li2O+K2O were 2.50%.

[0081] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 12.

[0082] Table 12: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0083] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0084] Example 13 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 61.78% SiO2, 8.50% B2O3, 16.50% Al2O3, 5.76% CaO, 2.78% SrO, 0.50% BaO, 1.50%MgO, 2.50% K2O, 0.00 Li2O, 0.18% SnO2; The composition of SiO2+B2O3+Al2O3 is 86.78%, MgO+CaO+BaO is 10.54%, and Li2O+K2O is 2.50%.

[0085] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 13.

[0086] Table 13: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0087] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0088] Example 14 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 66.01% SiO2, 5.50% B2O3, 17.10% Al2O3, 6.26% CaO, 2.56% SrO, 0.50% BaO, 1.68%MgO, 0.21% K2O, 0.00 Li2O, 0.18% SnO2; The percentages of SiO2+B2O3+Al2O3 were 88.61%, MgO+CaO+BaO were 11.00%, and Li2O+K2O were 0.21%.

[0089] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 14.

[0090] Table 14: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0091] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0092] Example 15 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 59.38% SiO2, 11.50% B2O3, 17.50% Al2O3, 6.05% CaO, 2.78% SrO, 0.70% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 88.38%, MgO+CaO+BaO are 11.23%, and Li2O+K2O are 0.25%.

[0093] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 15.

[0094] Table 15: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0095] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0096] Example 16 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 58.34% SiO2, 13.50% B2O3, 18.50% Al2O3, 4.48% CaO, 2.78% SrO, 0.70% BaO, 1.30% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 90.34%, MgO+CaO+BaO are 9.26%, and Li2O+K2O are 0.25%.

[0097] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 16.

[0098] Table 16: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0099] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0100] Example 17 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 59.45% SiO2, 11.20% B2O3, 19.50% Al2O3, 4.72% CaO, 2.63% SrO, 0.40% BaO, 1.70% MgO, 0.00 K2O, 0.25% Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 90.15%, MgO+CaO+BaO are 9.45%, and Li2O+K2O are 0.25%.

[0101] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 17.

[0102] Table 17: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0103] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0104] Example 18 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 59.37% SiO2, 12.50% B2O3, 17.50% Al2O3, 5.25% CaO, 2.78% SrO, 0.70% BaO, 1.50% MgO, 0.00 K2O, 0.25% Li2O, 0.15% SnO2; The composition of SiO2+B2O3+Al2O3 is 89.37%, MgO+CaO+BaO is 10.23%, and Li2O+K2O is 0.25%.

[0105] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 18.

[0106] Table 18: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0107] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0108] Example 19 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 58.17% SiO2, 13.50% B2O3, 17.50% Al2O3, 5.25% CaO, 2.78% SrO, 0.70% BaO, 1.70% MgO, 0.00 K2O, 0.25% Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 89.17%, MgO+CaO+BaO are 10.43%, and Li2O+K2O are 0.25%.

[0109] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 19.

[0110] Table 19: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0111] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0112] Example 20 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 58.97% SiO2, 14.50% B2O3, 15.50% Al2O3, 4.45% CaO, 2.78% SrO, 0.60% BaO, 1.80% MgO, 0.00 K2O, 0.25% Li2O, 0.15% SnO2; The composition of SiO2+B2O3+Al2O3 is 88.97%, MgO+CaO+BaO is 10.63%, and Li2O+K2O is 0.25%.

[0113] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 20.

[0114] Table 20: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0115] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0116] Example 21 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 56.97% SiO2, 16.50% B2O3, 16.50% Al2O3, 4.45% CaO, 2.78% SrO, 0.60% BaO, 1.80% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 89.97%, MgO+CaO+BaO are 9.63%, and Li2O+K2O are 0.25%.

[0117] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 21.

[0118] Table 21: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0119] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0120] Example 22 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 55.98% SiO2, 18.50% B2O3, 14.50% Al2O3, 5.54% CaO, 2.78% SrO, 0.60% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The composition of SiO2+B2O3+Al2O3 is 88.98%, MgO+CaO+BaO is 10.62%, and Li2O+K2O is 0.25%.

[0121] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 22.

[0122] Table 22: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0123] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0124] Example 23 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 53.88% SiO2, 20.50% B2O3, 13.50% Al2O3, 6.54% CaO, 2.78% SrO, 0.70% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 87.88%, MgO+CaO+BaO are 11.72%, and Li2O+K2O are 0.25%.

[0125] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 23.

[0126] Table 23: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0127] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0128] Example 24 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 50.25% SiO2, 22.50% B2O3, 17.50% Al2O3, 5.25% CaO, 2.45% SrO, 0.70% BaO, 1.20% MgO, 0.00 K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 90.25%, MgO+CaO+BaO are 9.60%, and Li2O+K2O are 0.00%.

[0129] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 24.

[0130] Table 24: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0131] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0132] Example 25 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 47.10% SiO2, 24.50% B2O3, 17.50% Al2O3, 5.25% CaO, 2.78% SrO, 0.70% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.22% SnO2; The composition of SiO2+B2O3+Al2O3 is 89.10%, MgO+CaO+BaO is 10.43%, and Li2O+K2O is 0.25%.

[0133] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 25.

[0134] Table 25: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0135] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0136] Example 26 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 43.10% SiO2, 30.50% B2O3, 15.50% Al2O3, 5.25% CaO, 2.78% SrO, 0.70% BaO, 1.70% MgO, 0.25% K2O, 0.00 Li2O, 0.22% SnO2; The composition of SiO2+B2O3+Al2O3 is 89.10%, MgO+CaO+BaO is 10.43%, and Li2O+K2O is 0.25%.

[0137] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 26.

[0138] Table 26: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0139] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0140] Example 27 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 63.39% SiO2, 11.20% B2O3, 15.50% Al2O3, 4.83% CaO, 2.98% SrO, 0.50% BaO, 1.20% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 are 90.09%, MgO+CaO+BaO are 9.51%, and Li2O+K2O are 0.25%.

[0141] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 27.

[0142] Table 27: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0143] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0144] Example 28 This embodiment provides a low coefficient of thermal expansion alkali-free borosilicate glass, with the following component contents by mass percentage: 57.91% SiO2, 11.50% B2O3, 19.50% Al2O3, 5.25% CaO, 3.28% SrO, 0.70% BaO, 1.46% MgO, 0.25% K2O, 0.00 Li2O, 0.15% SnO2; The percentages of SiO2+B2O3+Al2O3 were 88.91%, MgO+CaO+BaO were 10.69%, and Li2O+K2O were 0.25%.

[0145] The performance of the low expansion coefficient alkali-free borosilicate glass of this embodiment was tested, and the corresponding results are shown in Table 28.

[0146] Table 28: Performance Test Results of Alkali-Free Borosilicate Glass with Low Coefficient of Expansion

[0147] The above results demonstrate that the low expansion coefficient alkali-free borosilicate glass of this embodiment possesses excellent comprehensive performance and meets the parameter requirements of this application.

[0148] Based on the above results, the Tg range of low expansion coefficient alkali-free borosilicate glass is 639~749 ℃, the Ts range is 712~845 ℃, and the expansion coefficient (20~300℃) is 30~38*10. -7The dielectric constant is 64~76 GPa, elastic modulus is 25.76~30.92 GPa, Poisson's ratio is 0.21~0.25, dielectric constant (1 GHz) is 4.38~5.66 F / m, dielectric constant (5.2 GHz) is 4.35~5.59 F / m, and dielectric loss (1 GHz) is 1.961~4.801*10⁻⁶. -3 The dielectric loss (5.2 GHz) is 3.182~5.48*10. -3 The transmittance (550nm / 5mm) is 91.2%~92.51%, nd is 1.5018~1.5514, vd is 62.13~63.36, and density is 2.3563~2.4185g / cm³. 3 The Kirchert hardness is 393.1~440.3 kgf / m. 2 The above parameters meet the application requirements of encapsulation glass. When the content is optimized to SiO2 51%~65%, B2O3 10%~22%, Al2O3 14.5%~19%, CaO 2.3%~6.4%, SiO2+B2O3+Al2O3=86%~90%, MgO+CaO+BaO=9.5%~10.75%, the coefficient of thermal expansion (20~300 ℃) ranges from 31.5 to 35.72*10. -7 The elastic modulus is 66.98~76 GPa at ℃. When the content is optimized to 59%~63% SiO2, 10%~14.5% B2O3, and 17.5%~19% Al2O3, the coefficient of thermal expansion (20~300 ℃) ranges from 32.27 to 34.21 × 10⁻⁶. -7 The temperature is ℃, and the elastic modulus is 72.07~76 GPa. With the optimized process described in this application, those skilled in the art can select appropriate component ratios according to actual needs.

[0149] The low-expansion-coefficient alkali-free borosilicate glass of this invention features a rationally designed composition, exhibiting excellent thermal stability and a thermal expansion coefficient matching that of silicon. This reduces interfacial thermal stress, preventing warping, cracking, or interconnect failure, significantly improving the reliability and lifespan of 3D packaging. The glass also possesses excellent mechanical properties and good process tolerance, providing support for ultra-thin stacking. Its excellent electrical properties, with dielectric constant and dielectric loss results indicating its ability to reduce signal transmission delay and increase signal transmission speed in applications, further minimize energy loss and maintain signal integrity during transmission through the glass interlayer, contributing to reduced heat generation and bit error rate—crucial for high-frequency applications such as 5G and millimeter-wave. The low-expansion-coefficient alkali-free borosilicate glass exhibits high transmittance and excellent optical uniformity, demonstrating superior optical performance. Its suitable density facilitates lightweight equipment manufacturing, and its high hardness and resistance to water and acids provide direction for key materials in advanced packaging technologies.

[0150] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A low-expansion-coefficient alkali-free borosilicate glass, characterized in that, The product comprises the following components by mass percentage: SiO2 40%~70%, Al2O3 10%~20%, B2O3 5%~31%, MgO 0~3%, CaO 0~7%, SrO 0~2.5%, BaO 0~1%, K2O 0~0.25%, Li2O 0~0.25%, and SnO2 0~0.21%; the sum of the mass percentages of the above components is 100%; among which, the sum of the mass percentages of SiO2+B2O3+Al2O3 is 85%~91%, the sum of the mass percentages of MgO+CaO+BaO is 9%~12%, and the sum of the mass percentages of Li2O+K2O is 0~0.25%.

2. The low expansion coefficient alkali-free borosilicate glass according to claim 1, characterized in that, The product comprises the following components by mass percentage: SiO2 51%~65%, Al2O3 14.5%~19%, B2O3 10%~22%, MgO 0~3%, CaO 2.3~6.4%, SrO 0~2.5%, BaO 0~1%, K2O 0~0.25%, Li2O 0~0.25%, and SnO2 0~0.21%; the sum of the mass percentages of the above components is 100%; among which, the sum of the mass percentages of SiO2+B2O3+Al2O3 is 86%~90%, the sum of the mass percentages of MgO+CaO+BaO is 9.5%~10.75%, and the sum of the mass percentages of Li2O+K2O is 0~0.25%.

3. The low coefficient of thermal expansion alkali-free borosilicate glass according to claim 1, characterized in that, The product comprises the following components by mass percentage: SiO2 59%~63%, Al2O3 17.5%~19%, B2O3 10%~14.5%, MgO 0%~3%, CaO 2.3%~6.4%, SrO 0%~2.5%, BaO 0%~1%, K2O 0%~0.25%, Li2O 0%~0.25%, and SnO2 0%~0.21%; the sum of the mass percentages of the above components is 100%; among which, the sum of the mass percentages of SiO2+B2O3+Al2O3 is 85%~91%, the sum of the mass percentages of MgO+CaO+BaO is 9%~12%, and the sum of the mass percentages of Li2O+K2O is 0%~0.25%.

4. A method for preparing low-expansion-coefficient alkali-free borosilicate glass as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Mixing: Weigh all the raw materials according to the formula ratio, and then pour the raw materials into the mixer to mix them to obtain glass raw materials; (2) Melting: Add the glass raw material to the crucible, heat it to a certain temperature to melt it, then cool it down and stir it. After stirring, take out the stirrer and keep it warm for a certain time. (3) Molding: After the heat preservation and settling period, pour the molten glass into the hot mold; (4) Annealing: Finally, fine annealing is performed to eliminate stress and obtain low expansion coefficient alkali-free borosilicate glass.

5. The method for preparing low-expansion-coefficient alkali-free borosilicate glass according to claim 4, characterized in that: In step (1), the mixing time is 0.5~1.5 h.

6. The method for preparing low-expansion-coefficient alkali-free borosilicate glass according to claim 4, characterized in that: In step (2), the temperature is increased to 1550-1600℃ at a rate of 2-5℃ / min and then kept at that temperature for 5-10 hours.

7. The method for preparing low-expansion-coefficient alkali-free borosilicate glass according to claim 4, characterized in that: In step (2), the temperature is lowered to 1150~1300 ℃ and stirred for 4~9 h.

8. The method for preparing low-expansion-coefficient alkali-free borosilicate glass according to claim 4, characterized in that: In step (2), the temperature is kept stable for 0.5 to 2 hours.

9. The method for preparing low-expansion-coefficient alkali-free borosilicate glass according to claim 4, characterized in that: In step (3), the mold temperature is 650~750 ℃.

10. The method for preparing low-expansion-coefficient alkali-free borosilicate glass according to claim 4, characterized in that: In step (4), fine annealing is performed at 2~4 ℃ / h.

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