High thermal conductivity low temperature co-fired ceramic material and method of making

Abstract

The application discloses a low-temperature co-fired ceramic material with high thermal conductivity, which comprises a three-dimensional porous high-thermal-conductivity ceramic phase and a glass-ceramic phase filled in the pores of the high-thermal-conductivity ceramic phase, wherein the three-dimensional porous high-thermal-conductivity ceramic phase constitutes a heat conduction network inside the glass-ceramic phase, so as to solve the problems of poor phonon transmission path and interface thermal resistance. The preparation method is as follows: first, a three-dimensional porous carbon foam is used as a template, Al2O3 powder is added, nitrogen is introduced for a gas phase deposition reaction, AlN is deposited on the surface of the carbon foam, and then decarburization is carried out; then, CBS glass-ceramic slurry is filled and wrapped around the three-dimensional porous AlN, the sample is taken out after drying, the solvent and additives are removed by heating, and then sintering is carried out to obtain the low-temperature co-fired ceramic material with high thermal conductivity. The significant effect of the application is that the AlN with a three-dimensional interconnected network structure is implanted in the glass-ceramic, so as to form a perfect heat conduction path; meanwhile, the dielectric performance is not affected, and the thermal conductivity and the bending strength are significantly improved.

Description

Technical Field

[0001] This invention relates to microelectronic packaging technology, specifically to a low-temperature co-fired ceramic technology. Background Technology

[0002] Low Temperature Co-fired Ceramics (LTCC) is a novel microelectronic packaging technology primarily based on glass-ceramic or glass / ceramic two-phase composite materials. With its superior electrical, thermal, mechanical, and interconnect properties, LTCC has become the preferred method for miniaturization, integration, multifunctionality, and system-in-package (SiP) of next-generation passive devices. It is widely used in various microelectronic device fields, such as high-precision chip components, passive integrated functional devices, passive integrated substrates, and microelectronic functional modules.

[0003] In recent years, the development of system-in-package (SiP) towards high density, multifunctionality, high power, and intelligence has become an inevitable trend. However, with the continuous increase in integration density, the heat dissipation power density has risen sharply, making heat dissipation problems in microelectronic devices increasingly prominent and seriously threatening their reliability and lifespan. This places extremely stringent requirements on the heat dissipation performance of LTCC substrate materials. Therefore, the timely development of LTCC materials with excellent thermal conductivity plays a crucial role in improving the safety and reliability of microelectronic devices. Generally, the thermal conductivity of solid materials is closely related to the mean free path of their phonons. Glass materials exhibit short-range order and long-range disorder in their atomic arrangement, resulting in a relatively small mean free path of phonons in the glass matrix. This leads to low thermal conductivity in LTCC materials based on glass-ceramic or glass / ceramic two-phase composite materials. Currently, the thermal conductivity of typical glass-ceramic or glass / ceramic two-phase composite LTCC materials is only 2-3 W / mK, which is insufficient to meet the application requirements of large-scale and very large-scale integrated circuits.

[0004] Microelectronics engineers often enhance heat dissipation by adding a large number of metal thermal holes or microchannels inside the LTCC substrate when designing LTCC devices, in order to compensate for the low thermal conductivity of the LTCC substrate material. Although this method can improve the heat dissipation effect of LTCC packaged products to a certain extent, the processing technology is complex and the process is cumbersome.

[0005] Later, researchers selected highly thermally conductive ceramic phases (such as Al2O3, AlN, BN, Si3N4, and SiC) to mechanically mix with glass phases to prepare glass / ceramic multiphase LTCC materials, or added a certain proportion of highly thermally conductive fillers to the LTCC material system to improve the thermal conductivity of the LTCC material. Although this method can significantly improve the thermal conductivity of LTCC multiphase materials, it has the following fundamental problems that are difficult to solve:

[0006] ① In the preparation of multiphase materials, high thermal conductivity filler powder and matrix material powder are often mechanically mixed to prepare multiphase materials. Inside the multiphase material, the high thermal conductivity filler or ceramic phase is randomly dispersed in the matrix, lacking direct contact or interaction, which makes the phonon transport path unobstructed and limits the significant improvement of the thermal conductivity of the multiphase material. Although the thermal conductivity path can be formed by increasing the content of high thermal conductivity filler or ceramic phase, there is a lack of effective heat transfer path due to the interfacial thermal resistance between the high thermal conductivity filler and the glass matrix. Further increasing the filler content will greatly increase the interfacial area between the thermal conductivity filler and the glass matrix, causing the interfacial thermal resistance between the filler and the matrix to rise rapidly, affecting the thermal conductivity of the material.

[0007] ② To achieve high thermal conductivity, LTCC multiphase materials require a very high content of thermally conductive particles, generally exceeding 50 wt%, which must surpass the percolation threshold to form a complete thermal conduction pathway (N. Burger, A. Laachachi, M. Ferriol, M. Lutz, V. Toniazzo and D. Ruch. Review of thermalconductivity in composites: Mechanisms, parameters and theory[J]. Progress in Polymer Science, 2016, 61: 1-18.). This results in insufficient liquid phase content to completely encapsulate the high thermal conductivity filler or ceramic phase during sintering, severely affecting the densification of the LTCC material. Furthermore, the high content of thermally conductive particles makes them difficult to disperse in the matrix, significantly deteriorating other properties of the LTCC material (such as dielectric and mechanical properties). Summary of the Invention

[0008] This invention first provides a low-temperature co-fired ceramic material with high thermal conductivity, which includes a three-dimensional porous high thermal conductivity ceramic phase and a microcrystalline glass phase filling the pores of the high thermal conductivity ceramic phase. The three-dimensional porous high thermal conductivity ceramic phase forms a three-dimensional interconnected thermally conductive network inside the microcrystalline glass phase, so as to solve the problems of poor phonon transport pathways and interfacial thermal resistance caused by the lack of direct and effective contact or interaction between high thermal conductivity ceramics added by traditional mixing methods in the microcrystalline glass phase.

[0009] The high thermal conductivity ceramic phase is preferably AlN, and the microcrystalline glass phase is preferably CaO-B2O3-SiO2 microcrystalline glass. Based on the above preferences, a method for preparing a high thermal conductivity low-temperature co-fired ceramic material is as follows:

[0010] Step 1: Using three-dimensional porous carbon foam as a template, Al2O3 powder is added to it, and nitrogen gas is introduced to carry out a vapor phase deposition reaction, depositing AlN on the surface of the carbon foam.

[0011] Step 2: Decarburization yields three-dimensional porous AlN;

[0012] Step 3: Grind CaO-B2O3-SiO2 microcrystalline glass into CBS microcrystalline glass powder; disperse the CBS microcrystalline glass powder in a solvent, add additives, and mix well to form CBS microcrystalline glass slurry;

[0013] Step 4: Fill and encapsulate the three-dimensional porous AlN with CBS microcrystalline glass slurry, dry it, take out the sample, heat it to remove the solvent and additives, and then sinter it to obtain a high thermal conductivity low-temperature co-fired ceramic material. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the vapor-phase deposition process of AlN;

[0015] Figure 2 This is a microscopic morphology diagram of the three-dimensional network structure AlN;

[0016] Figure 3 XRD diffraction patterns of AlN and AlN / CBS with three-dimensional network structures;

[0017] Figure 4 Microscopic morphology of AlN / CBS;

[0018] Figure 5 This is the energy spectrum of AlN / CBS. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0020] Example 1:

[0021] A high thermal conductivity low-temperature co-fired ceramic material includes a three-dimensional porous high thermal conductivity ceramic phase and a microcrystalline glass phase filling the pores of the high thermal conductivity ceramic phase.

[0022] The high thermal conductivity ceramic phase can be any one of Al2O3, AlN, BN, Si3N4 and SiC; the microcrystalline glass phase is CaO-B2O3-SiO2 microcrystalline glass.

[0023] Among them, the three-dimensional porous high thermal conductivity ceramic phase is used to form a complete thermal conduction path with a three-dimensional interconnected network structure in glass-ceramics. Compared with the traditional addition (particle mixing) method of high thermal conductivity ceramics, it can significantly avoid the problems of poor phonon transport pathways and interface thermal resistance caused by lack of direct and effective contact.

[0024] Example 2:

[0025] A method for preparing a high thermal conductivity low-temperature co-fired ceramic material comprises the following steps:

[0026] Step 1, such as Figure 1 As shown, Al2O3 powder is added to the bottom of a cylindrical AlN crucible, and then three-dimensional porous carbon foam is placed on the Al2O3 powder. Nitrogen gas is introduced at a flow rate of 50-80 mL / min, and the crucible is heated to 1700-2000℃ and maintained for 10-15 h. The carbon foam is used as a template for vapor deposition reaction. At high temperature, the gaseous low-valence oxides of C and Al react with N2 to generate solid AlN and CO gas. AlN is gradually deposited on the surface of the porous interconnected carbon template, and finally a continuous AlN high thermal conductivity ceramic phase is deposited on the surface of the carbon foam.

[0027] Step 2: Place the composite of foamed carbon and AlN in a muffle furnace and heat to 600-700℃, then decarburize in air atmosphere for 2-5 hours to obtain three-dimensional porous AlN.

[0028] Step 3: Weigh out 30-50% CaO, 35-45% SiO2, and 10-20% B2O3 by mass. Mix the three together and pour into a platinum crucible. Place the platinum crucible in a muffle furnace at 1400-1600℃ and keep it at that temperature for 1-4 hours to obtain a high-temperature molten CaO-B2O3-SiO2 microcrystalline glass liquid. Remove the platinum crucible and quickly pour the glass liquid into deionized water for water quenching to obtain broken glass. Dry the broken glass and then crush it into 0.2mm glass particles using a crusher. Finally, use a planetary ball mill to obtain CBS microcrystalline glass powder with a particle size of 1.8-3.5μm.

[0029] The CBS microcrystalline glass powder is then dispersed in a solvent, which is one or more of ethanol, ethyl acetate, and butanone; then castor oil is added and the mixture is ball-milled for 4 hours to obtain a CBS microcrystalline glass suspension; then polymethyl methacrylate and butyl titanate are added to the CBS microcrystalline glass suspension, and the mixture is ball-milled for another 12 hours to obtain a CBS microcrystalline glass slurry.

[0030] The mass ratio of the CBS microcrystalline glass powder, solvent, castor oil, polymethyl methacrylate and butyl titanate is 50:18-24:1-1.2:3-4:1.5-2.1.

[0031] Step 4: Place the three-dimensional porous AlN in a mold (to facilitate the casting of CBS microcrystalline glass slurry), inject CBS microcrystalline glass slurry into the mold, dry it, heat it to 600-700℃ and keep it for 1-3 hours to remove additives, and then sinter it at 800-950℃ for 10-30 minutes to obtain a high thermal conductivity low-temperature co-fired ceramic material.

[0032] Example 3:

[0033] A method for preparing high thermal conductivity low-temperature co-fired ceramic materials:

[0034] First, three-dimensional porous AlN was prepared: Al2O3 powder was added to the bottom of an AlN crucible, and then three-dimensional porous carbon foam with a pore size of 100 ppi was placed on the Al2O3 powder. Nitrogen gas was introduced at a flow rate of 60 mL / min, and the crucible was heated to 1800±20℃ and held for 12 h. The carbon foam was used as a template for vapor deposition reaction, and finally a continuous AlN high thermal conductivity ceramic phase was deposited on the surface of the carbon foam. The composite of carbon foam and AlN was heated to 600℃ for decarburization for 3.5 h to obtain three-dimensional porous AlN.

[0035] The microstructure of three-dimensional porous AlN is as follows Figure 2 As shown, the XRD diffraction pattern is as follows: Figure 3 As shown; from Figure 2 , 3 It can be seen that the above vapor deposition method yielded a three-dimensional porous AlN material.

[0036] Secondly, CBS microcrystalline glass powder was prepared: CaO, SiO2, and B2O3 powders were weighed out, with mass fractions of 40%, 40%, and 20%, respectively; the three were mixed and poured into a platinum crucible, which was then placed in a muffle furnace at 1500±15℃ and kept at that temperature for 3 hours to obtain a high-temperature molten CaO-B2O3-SiO2 microcrystalline glass liquid. The platinum crucible was removed, and a portion of the glass liquid was quickly poured into deionized water for quenching to obtain broken glass. The broken glass was dried, crushed, and ball-milled to obtain CBS microcrystalline glass powder; the remaining glass liquid was poured into a mold and allowed to cool naturally to obtain CBS microcrystalline glass.

[0037] Next, four groups of CBS microcrystalline glass slurries (represented by Experiment Examples 1, 2, 3, and 4) were prepared: CBS microcrystalline glass powder was dispersed in a solvent, castor oil was added, and the mixture was ball-milled. After 4 hours, polymethyl methacrylate and butyl titanate were added, and ball milling continued for 12 hours to obtain the CBS microcrystalline glass slurry. The composition and content of the four groups of CBS microcrystalline glass slurries are shown in Table 1.

[0038] Table 1. Composition of CBS Microcrystalline Glass Slurry (Unit: grams)

[0039]

[0040] Finally, the three-dimensional porous AlN obtained in step one was placed in a mold, and four sets of CBS microcrystalline glass slurry were injected into the mold to completely fill the network pores inside the AlN. After drying, the AlN was heated to 600℃ and held for 2 hours, and then sintered at 800℃ for 20 minutes to remove organic matter, resulting in high thermal conductivity low-temperature co-fired ceramics 1, 2, 3, and 4.

[0041] Example 4:

[0042] A method for preparing high thermal conductivity low-temperature co-fired ceramic materials:

[0043] First, three-dimensional porous AlN was prepared: Al2O3 powder was added to the bottom of an AlN crucible, and then three-dimensional porous carbon foam was placed on the Al2O3 powder. The carbon foam was cylindrical and four pore sizes of 50ppi, 70ppi, 100ppi and 120ppi were selected. Nitrogen gas was introduced at a flow rate of 60mL / min, the crucible was heated to 1800±20℃ and held for 12h, and the carbon foam was used as a template for vapor deposition reaction. Finally, a continuous AlN high thermal conductivity ceramic phase was deposited on the surface of the carbon foam. The composite of carbon foam and AlN was heated to 600℃ for decarburization for 3.5h to obtain four sizes of three-dimensional porous AlN, which were named AlN-1 (50ppi), AlN-2 (70ppi), AlN3- (100ppi) and AlN4- (120ppi). The three-dimensional porous AlN was also cylindrical.

[0044] Secondly, prepare CBS microcrystalline glass slurry: Take 50g of CBS microcrystalline glass powder prepared in Example 3 and place it in a nylon can. Add 10g of ethanol and 10g of butanone as a mixed solvent, then add 1g of castor oil and 200g of zirconia balls. Place it in a planetary ball mill and disperse for 4 hours. Then add 3.5g of polymethyl methacrylate and 1.75g ​​of butyl titanate and continue to ball mill for 12 hours to obtain a high solids content CBS microcrystalline glass slurry.

[0045] Finally, four sizes of three-dimensional porous AlN were placed in four glass dishes of the same size, keeping the centerline of the cylindrical AlN vertical. CBS microcrystalline glass slurry was poured into each dish until it reached the same height as the AlN, and then left to stand at room temperature for 12 hours to allow the slurry to completely fill the network voids of the AlN and to basically dry and set. The mixture was then heated in a muffle furnace at 650℃ for 1-3 hours to remove organic additives, and finally sintered at 800℃ for 30 minutes to obtain AlN / CBS microcrystalline glass LTCC multiphase materials with a three-dimensional interconnected thermally conductive network, denoted as AlN-1 / CBS, AlN-2 / CBS, AlN-3 / CBS, AlN-4 / CBS, and AlN-3 / CBS, respectively. The XRD diffraction patterns of AlN-3 / CBS are shown below. Figure 3 As shown; the microstructure of AlN-3 / CBS is as follows. Figure 4 As shown, the energy spectrum is shown in the image. Figure 5 .from Figure 3 , 4 From point 5, we can see that CBS glass-ceramics cross-link with the AlN network to form an AlN / CBS glass-ceramics composite material. The dielectric properties, mechanical strength, and thermal conductivity of the CBS glass-ceramics and the four composite materials were measured, and the results are shown in Table 2.

[0046] Table 2. Statistical Table of Performance Parameters of CBS Microcrystalline Glass and AlN / CBS Multiphase Materials

[0047]

[0048] As shown in Table 2, thanks to the three-dimensional interconnected network structure of AlN forming a complete thermal conductivity path in the composite material, the thermal conductivity of AlN / CBS composite materials can be significantly increased from 2.2 W / mK to 10.1-13.8 W / mK with a relatively low AlN addition amount (only 16.2-21.4%). At the same time, the three-dimensional interconnected network of AlN can also significantly improve the flexural strength of AlN / CBS composite materials, and has little impact on dielectric properties, resulting in excellent dielectric properties of AlN / CBS composite materials.

[0049] Beneficial effects: By implanting AlN with a three-dimensional interconnected network structure into the microcrystalline glass, a perfect heat conduction path is formed; while avoiding affecting the dielectric properties, the thermal conductivity and bending strength are significantly improved.

[0050] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A high thermal conductivity low-temperature co-fired ceramic material, characterized in that: It includes a three-dimensional porous high thermal conductivity ceramic phase and a microcrystalline glass phase filling the pores of the high thermal conductivity ceramic phase; The high thermal conductivity ceramic phase is AlN, and the microcrystalline glass phase is CaO-B2O3-SiO2 microcrystalline glass.

2. A method for preparing a high thermal conductivity low-temperature co-fired ceramic material as described in claim 1, characterized in that... Follow these steps: Step 1: Using three-dimensional porous carbon foam as a template, Al2O3 powder is added to it, and nitrogen gas is introduced to carry out a vapor phase deposition reaction, depositing AlN on the surface of the carbon foam. Step 2: Decarburization yields three-dimensional porous AlN; Step 3: Grind CaO-B2O3-SiO2 microcrystalline glass into CBS microcrystalline glass powder; disperse the CBS microcrystalline glass powder in a solvent, add additives, and mix well to form CBS microcrystalline glass slurry; Step 4: Fill and encapsulate the three-dimensional porous AlN with CBS microcrystalline glass slurry, dry the sample, remove the solvent and additives by heating, and then sinter to obtain a high thermal conductivity low-temperature co-fired ceramic material.

3. The method for preparing high thermal conductivity low-temperature co-fired ceramic materials according to claim 2, characterized in that: In step one, Al2O3 powder is added to the bottom of the crucible, and then foamed carbon is placed on the Al2O3 powder. Under a nitrogen atmosphere with a flow rate of 50-80 mL / min, the mixture is heated to 1700-2000℃ and held for 10-15 h to deposit AlN on the surface of the foamed carbon.

4. The method for preparing high thermal conductivity low-temperature co-fired ceramic materials according to claim 2, characterized in that: In step two, decarburization is carried out at 600-700℃ for 2-5 hours to obtain three-dimensional porous AlN.

5. The method for preparing high thermal conductivity low-temperature co-fired ceramic materials according to claim 2, characterized in that: In step three, CaO-B2O3-SiO2 microcrystalline glass is prepared using a high-temperature melting-water quenching method. The CaO-B2O3-SiO2 microcrystalline glass is composed of the following components by mass percentage: CaO is 30-50% by mass, SiO2 is 35-45% by mass, and B2O3 is 10-20% by mass, with each component accounting for 100% by mass. The solvent is one or more selected from ethanol, ethyl acetate, and butanone; The additives in the CBS microcrystalline glass slurry also include castor oil, polymethyl methacrylate and butyl titanate; The mass ratio of the CBS microcrystalline glass powder, solvent, castor oil, polymethyl methacrylate and butyl titanate is 50:18-24:1-1.2:3-4:1.5-2.

1.

6. The method for preparing high thermal conductivity low-temperature co-fired ceramic materials according to claim 5, characterized in that: In step three, CBS microcrystalline glass powder is first dispersed in a solvent, and then castor oil is added and ball-milled for 4 hours to obtain a CBS microcrystalline glass suspension. Then, polymethyl methacrylate and butyl titanate were added to the CBS microcrystalline glass suspension, and ball milling was continued for 12 hours to obtain CBS microcrystalline glass slurry.

7. The method for preparing high thermal conductivity low-temperature co-fired ceramic materials according to claim 2, characterized in that: In step four, three-dimensional porous AlN is placed in a mold, CBS microcrystalline glass slurry is injected into the mold, and after standing and drying, it is heated to 600-700℃ and held for 1-3 hours, and then sintered at 800-950℃ for 10-30 minutes to obtain a high thermal conductivity low-temperature co-fired ceramic material.

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