High-density high-strength ltcc green sheet, and preparation method and application thereof

Abstract

The application belongs to the technical field of low-temperature co-fired ceramic and particularly relates to a high-density high-strength LTCC green ceramic sheet and a preparation method and application thereof. The preparation method comprises that the raw material is fully mixed and then flow-cast shaped, the equivalent particle size ratio of the packing phase powder to the filling phase powder is 1:(0.4-0.8), and the volume ratio of the packing phase powder to the filling phase powder is 1:(0.15-0.45). The high-density high-strength LTCC green ceramic sheet is used for preparing a low-temperature co-fired ceramic substrate. The technical scheme provided by the application realizes low porosity in the sintered substrate on the basis of not changing the substrate raw material composition or whisker, and further realizes the effect of improving the bending strength while other performances are not affected by fully mixing the inorganic powder with different particle sizes and matching the dosage ratio of the two.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature co-fired ceramics technology, specifically relating to a high-density, high-strength LTCC green ceramic sheet, its preparation method, and its application. Background Technology

[0002] Low-Temperature Cofired Ceramic (LTCC) meets the development trend of modularization and integration of electronic components, and its application in the semiconductor packaging field has become increasingly widespread in recent years. The trend towards miniaturization and high integration in packaging places higher demands on the bending strength of LTCC substrates. LTCC green ceramic sheets are the most basic functional material for LTCC substrates, typically prepared by ball milling and mixing glass powder, ceramic powder, binder, dispersant, plasticizer, and solvent, followed by casting. LTCC substrates are then manufactured through processes such as lamination, isostatic pressing, and sintering of the green ceramic sheets.

[0003] Existing methods for strengthening LTCC substrates mainly include: changing the composition of glass powder or ceramics to increase the Young's modulus of the material; introducing dendritic fibers / whiskers to improve substrate strength through pull-out effect; and increasing material density and reducing porosity. However, the first two methods alter the composition of the LTCC substrate, affecting the dielectric constant and dielectric damage while increasing strength.

[0004] Chinese patent CN116217254A discloses a fiber-reinforced LTCC substrate. In order to avoid the adverse effects of heterogeneous fillers on the key performance of the substrate, it selects glass fiber of the same material as the LTCC substrate as a reinforcing filler to improve the strength of the substrate. However, this solution may induce the drawback of inconsistent X / Y shrinkage rates during sintering.

[0005] Porosity is the main factor affecting the strength of a substrate. When the porosity is similar, the crystalline phase content will affect the bending strength. However, there is currently little publicly available information on how to prepare high-density LTCC substrate materials using the LTCC system. Summary of the Invention

[0006] This invention provides a high-density, high-strength LTCC green ceramic sheet, its preparation method, and its application, in order to solve the problem that increasing the bending strength of LTCC substrates leads to a deterioration in key performance characteristics.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for preparing the high-density and high-strength LTCC green ceramic sheet, which includes the following steps: fully mixing the bulk phase powder and the filler phase powder in the raw material and then casting it into a sheet, wherein the equivalent particle size ratio of the bulk phase powder to the filler phase powder is 1:(0.4-0.8), and the volume ratio of the bulk phase powder to the filler phase powder is 1:(0.15-0.45).

[0008] Optionally, the equivalent particle size ratio of the packed phase powder to the filled phase powder is 1:(0.5-0.6), and the volume ratio of the packed phase powder to the filled phase powder is 1:(0.35-0.45).

[0009] Optionally, the particle size distribution span (D90-D10) / D50 of the packed phase powder is less than 0.7, and the particle size distribution span (D90-D10) / D50 of the filled phase powder is less than 0.7.

[0010] Optionally, the accumulated phase powder is selected from one or more of aluminum nitride, aluminum oxide, cordierite and mullite.

[0011] Optionally, the filler phase powder is microcrystalline glass powder.

[0012] Optionally, the filler phase powder comprises one or more of the following components: CaO (calcium oxide), SiO2 (silicon oxide), B2O3 (boron oxide), Al2O3 (aluminum oxide), Li2O (lithium oxide), and K2O (potassium oxide).

[0013] Optionally, the total amount of CaO, SiO2, and B2O3 in the filler phase powder is 80-100 wt% by weight.

[0014] Optionally, the packed phase powder is spherical particles, and the filling phase powder is spherical or ellipsoidal particles.

[0015] Optionally, the equivalent particle size of the packed phase powder is 2-7 μm, preferably 3-6 μm.

[0016] Optionally, the raw materials further include binders, plasticizers, dispersants and solvents, wherein the total volume ratio of the binder and plasticizer to the total volume ratio of the bulked phase powder is (0.45-0.75):1, preferably (0.5-0.6):1.

[0017] In raw ceramics, there are still pores between the accumulated phase and the filling phase. The purpose of this ratio is to fill these pores. If there is too much, it may overflow, which is detrimental to the sintering strength.

[0018] Optionally, the binder is selected from PVB (polyvinyl butyral), the plasticizer is selected from DBP (dibutyl phthalate), the dispersant is selected from castor oil, and the solvent is a mixture of xylene and ethanol.

[0019] Optionally, the bulk phase powder, filler phase powder, solvent and dispersant in the raw materials are mixed and then ball-milled for 20-30 hours; then binder and plasticizer are added and ball-milled for 20-30 hours; finally, the slurry is cast into shape.

[0020] The present invention also provides a high-density and high-strength LTCC green ceramic sheet, which is prepared by the above-mentioned method for preparing high-density and high-strength LTCC green ceramic sheets.

[0021] The present invention also provides a low-temperature co-fired ceramic substrate, which is prepared by using the above-mentioned high-density and high-strength LTCC green ceramic sheets as raw materials and through stacking, isostatic pressing, debinding and sintering processes.

[0022] Optionally, the debinding temperature is 400-500℃, and the sintering temperature is 800-900℃.

[0023] The technical solution provided by this invention has the following advantages compared with the prior art: by using two inorganic powders with different particle sizes and matching their dosage ratio, the raw ceramic sheet material can be fully mixed and tightly arranged. Without changing the composition of the substrate material or whiskers, a low porosity in the sintered substrate is achieved, thereby improving the bending strength while keeping other properties unaffected. Detailed Implementation

[0024] For ease of understanding, the high-density, high-strength LTCC green ceramic sheets, their preparation methods, and applications are described below with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] Example 1

[0026] The raw material composition and preparation method of the raw ceramic slabs are as follows:

[0027] LTCC powders include packed phase powders and filled phase powders.

[0028] The bulking phase powder was mullite (purchased from Daihan Refractories Manufacturing, Seoul, Korea, and sieved in-house), with an equivalent particle size of 3.4 μm and a span value of 0.65.

[0029] Filler phase powder: microcrystalline glass powder (self-made, 27wt% CaO, 45wt% SiO2, 27wt% B2O3, 1mol% Li2O), equivalent particle size 2μm, Span value 0.63.

[0030] The volume ratio of microcrystalline glass powder to mullite is 0.41, and the particle size ratio is 0.59.

[0031] Binder: PVB, particle size <4μm; Plasticizer: DBP.

[0032] The total volume ratio of binder and plasticizer to LTCC powder is 0.6.

[0033] Dispersant: Castor oil, with a volume ratio of 0.30 to LTCC powder.

[0034] Solvent: a xylene-ethanol mixture in a volume ratio of 1:1 with LTCC powder.

[0035] After ball milling LTCC powder, solvent, and dispersant for 24 hours, binder and plasticizer are added and ball milled for 24 hours. The slurry is then cast to obtain the high-density, high-strength LTCC green ceramic sheet.

[0036] The high-density, high-strength LTCC green ceramic sheets prepared above are then stacked, isostatically pressed, debinded, and sintered to obtain LTCC substrates.

[0037] The debinding temperature is 500 degrees Celsius, and the sintering temperature is 850 degrees Celsius.

[0038] Example 2

[0039] The raw material composition and preparation method of the raw ceramic slabs are as follows:

[0040] LTCC powders include packed phase powders and filled phase powders.

[0041] The packed phase powder was alumina (Japan Light Metals, SA43A, sieved in-house), with an equivalent particle size of 3.2 μm and a span value of 0.55.

[0042] Filler phase powder: microcrystalline glass powder (self-made, 18wt% CaO, 50wt% SiO2, 12wt% Al2O3, 15wt% B2O3, 5wt% K2O), equivalent particle size 1.8μm, Span value 0.67.

[0043] The volume ratio of microcrystalline glass powder to alumina is 0.45, and the particle size ratio is 0.56.

[0044] Binder: PVB, particle size <4μm; Plasticizer: DBP.

[0045] The total volume ratio of binder and plasticizer to LTCC powder is 0.56.

[0046] Dispersant: Castor oil, with a volume ratio of 0.30 to LTCC powder.

[0047] Solvent: a xylene-ethanol mixture in a volume ratio of 1:1 with LTCC powder.

[0048] After ball milling LTCC powder, solvent, and dispersant for 24 hours, binder and plasticizer are added and ball milled for 24 hours. The slurry is then cast to obtain the high-density, high-strength LTCC green ceramic sheet.

[0049] The high-density, high-strength LTCC green ceramic sheets prepared above are then stacked, isostatically pressed, debinded, and sintered to obtain LTCC substrates.

[0050] The glue removal temperature is 500℃, and the sintering temperature is 875℃.

[0051] Comparative Example 1

[0052] The difference from Example 1 is that the mullite particle size is 1.9 μm, which means that the particle size ratio of the filler phase powder to the bulk phase powder is approximately 1:1.

[0053] Comparative Example 2

[0054] The difference from Example 1 is that the mullite has a particle size distribution Span value of 2.2.

[0055] Comparative Example 3

[0056] The difference from Example 1 is that the particle size distribution Span value of the microcrystalline glass powder is 2.8.

[0057] Comparative Example 4

[0058] The difference from Example 1 is that the volume ratio of microcrystalline glass powder to mullite is 0.23.

[0059] Comparative Example 5

[0060] The difference from Example 1 is that the mullite is an ellipsoidal particle, and the SEM measurement results show that the ratio of major axis to minor axis is about 1.5.

[0061] Comparative Example 6

[0062] The difference from Example 2 is that the packed phase is alumina (Japan Light Metals, SA41A, particle size 1.2 micrometers), that is, the particle size ratio of the filler phase powder to the packed phase powder is 0.38.

[0063] Performance Experiment

[0064] 1. Substrate density: The substrate density was measured using Archimedes' displacement method.

[0065] 2. Bending strength: The bending strength of the substrate shall be measured in accordance with GB / T 6569—2006.

[0066] 3. Equivalent particle size: The equivalent particle size is measured using a laser particle size analyzer.

[0067] 4. Particle size distribution: The particle size distribution span (Span value) is calculated using particle size distribution data from a laser particle size analyzer.

[0068] That is, (D90-D10) / D50.

[0069] 5. Dielectric constant and dielectric loss shall be tested in accordance with GB / T 5594.4-2015 standard.

[0070] The LTCC substrates prepared in Examples 1 and 2 and Comparative Examples 1-5 were subjected to the above performance tests, and the experimental data are shown in Table 1.

[0071] Table 1

[0072] Substrate density (g / cm3) Flexural strength (MPa) Dielectric constant 1MHz Dielectric loss 1MHz Example 1 2.89 150 4.8 0.016 Example 2 3.1 226 6.5 0.003 Comparative Example 1 2.65 103 4.0 0.025 Comparative Example 2 2.71 123 4.6 0.019 Comparative Example 3 2.72 130 4.7 0.019 Comparative Example 4 2.58 53 3.2 0.223 Comparative Example 5 2.80 136 4.1 0.018 Comparative Example 6 2.66 119 4.5 0.020

[0073] In summary, by comparing Example 1 with Comparative Examples 1-5, it can be found that the particle size ratio of the filled phase powder to the packed phase powder, the particle size distribution and shape of the filled / packed phase powder, and the volume ratio of the filled phase powder to the packed phase powder all affect the basic density, flexural strength, dielectric constant, and dielectric loss. Among these, the volume ratio of the filled phase powder to the packed phase powder has the greatest impact. Furthermore, by comparing Example 2 and Comparative Example 6, it can be found that changes in the particle size ratio of the filled phase powder to the packed phase powder also significantly affect various performance parameters.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-density, high-strength LTCC green ceramic tiles, characterized in that, The process includes the following steps: thoroughly mixing the bulk phase powder and the filler phase powder in the raw material and then casting it into shape, wherein the equivalent particle size ratio of the bulk phase powder to the filler phase powder is 1:(0.5-0.6), and the volume ratio of the bulk phase powder to the filler phase powder is 1:(0.35-0.45). The packed phase powder is alumina, the filling phase powder is microcrystalline glass powder, and the filling phase powder is calculated by weight percentage as 18wt% CaO, 50wt% SiO2, 12wt% Al2O3, 15wt% B2O3 and 5wt% K2O. The particle size distribution span (D90-D10) / D50 of the packed phase powder is less than 0.7, and the particle size distribution span (D90-D10) / D50 of the filled phase powder is less than 0.

7.

2. The method for preparing high-density, high-strength LTCC green ceramic sheets according to claim 1, characterized in that, The packed phase powder is spherical particles, and the filling phase powder is spherical or ellipsoidal particles.

3. The method for preparing high-density, high-strength LTCC green ceramic sheets according to claim 1, characterized in that, The equivalent particle size of the packed phase powder is 2-7 μm.

4. The method for preparing high-density, high-strength LTCC green ceramic sheets according to claim 3, characterized in that, The equivalent particle size of the packed phase powder is 3-6 μm.

5. The method for preparing high-density, high-strength LTCC green ceramic sheets according to claim 1, characterized in that, The raw materials also include binders, plasticizers, dispersants and solvents, and the total volume ratio of the binders and plasticizers to the total volume of the bulked phase powder is (0.45-0.75):

1.

6. The method for preparing high-density, high-strength LTCC green ceramic sheets according to claim 5, characterized in that, The ratio of the total volume of the binder and plasticizer to the total volume of the bulked phase powder is (0.5-0.6):

1.

7. The method for preparing high-density, high-strength LTCC green ceramic sheets according to claim 5, characterized in that, The binder is selected from PVB, the plasticizer is selected from DBP, the dispersant is selected from castor oil, and the solvent is a mixture of xylene and ethanol.

8. A high-density and high-strength LTCC green ceramic tile, characterized in that, It is prepared using the preparation method of high-density, high-strength LTCC green ceramic sheet as described in any one of claims 1-7.

9. A low-temperature co-fired ceramic substrate, characterized in that, The material is LTCC green ceramic sheet as described in claim 8, which is prepared by stacking, isostatic pressing, debinding and sintering.