A method for manufacturing a micro LTCC filter

Abstract

The application discloses a preparation method of a micro LTCC filter and belongs to the technical field of filter preparation. The preparation method comprises the following steps: first, electrode silver paste is used as raw material to print and prepare the first layer of electrode patterns on a transfer film; then, ceramic paste and electrode silver paste are alternately used as raw material to respectively perform laminated printing and drying to prepare dielectric layers and electrode patterns to obtain a blank body; then, drying, cutting, degassing and sintering are performed; and finally, post-processing technology is performed to obtain the micro LTCC filter. The micro LTCC filter is prepared by replacing the traditional LTCC preparation process with the ceramic paste lamination method, so that the shrinkage difference in the processing process is reduced, the fixed shrinkage rate can be calculated to design the proportion of the dielectric layer and the metal electrode before and after sintering when the micro product is prepared, the difference between the designed product and the actual product is smaller, the design error is reduced, high-end precision equipment is not required in the preparation process, the manufacturing process is shorter, and the method is suitable for large-scale and rapid production.

Description

Technical Field

[0001] This invention relates to the field of filter fabrication technology, and specifically to a method for fabricating a micro-sized LTCC filter. Background Technology

[0002] LTCC filters, operating in the frequency range of 300kHz to 300GHz, are low-pass filter circuits composed of inductors and capacitors. They allow the current of useful signals to pass through while significantly attenuating higher-frequency interference signals. Therefore, they are commonly used as wireless radio frequency components in mobile communication devices, such as mobile phones, WLAN, Bluetooth, power amplifiers, and automotive electronics. With increasing market demand and functional requirements, miniaturization of LTCC filters is a future trend.

[0003] LTCC is a 3D structure consisting of a dielectric layer and metal electrodes. The dielectric layer is produced by ball milling ethanol, toluene, polyether phosphate, polyvinyl butyral, diisobutyl phthalate, and LTCC microwave dielectric ceramic powder in a specific ratio to create a ceramic slurry. The ceramic slurry is then degassed under vacuum and cast on a casting machine. During the casting process, a carrier film is used to coat the ceramic slurry onto the carrier film, which is then dried to obtain a roll of LTCC green ceramic tape with a thickness of 20μm to 90μm. The solid content of the ceramic powder in the ceramic slurry can reach 40% to 60%.

[0004] Because LTCC has a three-dimensional design structure, to achieve the circuit design and through-conductivity requirements of each layer, it needs to be processed using sheet-shaped green ceramic tapes. Therefore, existing manufacturing methods mainly utilize rolled green ceramic tapes for cutting into sheet-shaped green ceramic tapes. Then, circuit patterns are prepared through laser drilling, silver paste injection into micro-holes, and precision printing. After heating and drying the circuit patterns, green ceramic tapes covered with metal electrodes are obtained. Multiple sheets of green ceramic tapes with metal electrodes are heated, dried, and stacked. After cutting into granules, adhesive is removed, and sintering occurs. Finally, post-processing processes such as edge rolling, end silvering, sintering, electroplating, external inspection, and packaging are used to produce LTCC filter products. Figure 1 As shown. Due to future design requirements, the fabrication of LTCC filters will gradually shift towards miniaturized LTCC filters. However, due to variations in multiple processes during LTCC filter fabrication, particularly the differences in precision between miniaturized and large-size LTCC filters, more precise high-end equipment or superior fabrication methods are needed to reduce shrinkage differences between the green ceramic tape and electrode silver paste, as well as alignment deviations during green ceramic tape stacking. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for fabricating miniature LTCC filters, thereby resolving the issue that existing miniature LTCC filters rely on sophisticated high-end equipment and lack convenient manufacturing methods.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] A method for fabricating a miniature LTCC filter includes the following steps:

[0008] First, electrode pattern is printed on a transfer film using electrode silver paste as raw material. Then, ceramic paste and electrode silver paste are used alternately as raw materials to print and dry the dielectric layer and electrode pattern to obtain a blank. Then, the blank is dried, cut, debinded and sintered, and finally processed by post-processing.

[0009] Furthermore, the fourth layer is a dielectric layer with holes, and the fifth layer is an electrode pattern that fills or prints the holes in the fourth layer. The preparation of the fourth and fifth layers is repeated several times until the target number of layers is reached. Then, the top layer is prepared using ceramic paste as raw material. The target number of layers is 5+2n, where n = 0 to 100.

[0010] Furthermore, the transfer film includes OPP film or release PET film.

[0011] Furthermore, the solid content of the electrode silver paste is 75–92 wt%.

[0012] Further, the ceramic paste is prepared by mixing the following components in parts by weight: 75-92 parts of LTCC microwave dielectric ceramic powder, 1-5 parts of polyacrylamide butyral resin, 1-5 parts of polyester, 5-15 parts of diethylene glycol monobutyl ether acetate and 5-15 parts of terpineol.

[0013] The LTCC microwave dielectric ceramic powder comprises the following components by weight: 50-60 parts SiO2, 40-50 parts Al2O3, 0.5-2 parts B2O3, and 1-3 parts TiO2.

[0014] Furthermore, the solid content of the ceramic paste is 75–92 wt%, and the viscosity of the ceramic paste is 100,000–600,000 Cp.

[0015] Furthermore, the drying temperature for each layer after printing is 40–100℃, and the drying time is 5–15 minutes.

[0016] Furthermore, the thickness of each layer is 5–120 μm.

[0017] Furthermore, the temperature for debinding is 250–450℃, and the time is 1–5 hours; the temperature for sintering is 850–950℃, and the time is 1–5 hours.

[0018] Furthermore, post-processing techniques include edge rolling, silver finishing, sintering, and electroplating.

[0019] The present invention has the following beneficial effects:

[0020] This invention uses ceramic paste instead of ceramic slurry casting in the traditional manufacturing process to prepare micro-LTCC filters, reducing shrinkage differences during processing. When preparing micro-sized products, the shrinkage rate can be fixed to calculate the design ratio of the dielectric layer and metal electrode before and after sintering, making the difference between the designed product and the actual product smaller and reducing design errors. The preparation process does not require high-end precision equipment, the production process is shorter, and it is suitable for large-scale rapid production. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the fabrication process of LTCC filters using traditional techniques.

[0022] Figure 2 This is a flowchart illustrating the fabrication process of the miniature LTCC filter of the present invention.

[0023] Figure 3 This is a schematic diagram of the overprinting method during the fabrication of the miniature LTCC filter of the present invention. Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0025] Example 1:

[0026] A method for fabricating micro-LTCC filters (fabrication flowchart shown) Figure 2 As shown in the diagram, the overprinting process is illustrated below. Figure 3 (As shown), including the following steps:

[0027] (1) Preparation of ceramic paste with a solid content of 80wt%: 80 parts of LTCC microwave dielectric ceramic powder, 3 parts of polyacrylamide butyral resin, 3 parts of polyester, 7 parts of diethylene glycol monobutyl ether acetate and 7 parts of terpineol are mixed by weight and mixed evenly by three drums and centrifugal mixer to obtain the paste.

[0028] The LTCC microwave dielectric ceramic powder comprises the following components by weight: 54 parts SiO2, 43 parts Al2O3, 1 part B2O3, and 2 parts TiO2.

[0029] (2) Preparation of the first layer: Using release PET film as transfer film on printing equipment, electrode silver paste (manufacturer: NAMICS CORPORATION; model: 7396; solid content 85%) is used as raw material. A screen is placed on the transfer film to print the electrode pattern. The printing thickness is 15μm. After printing, it is placed in an oven and dried at 80℃ for 10min to complete the external circuit electrode and obtain the first layer.

[0030] (3) Preparation of the second layer: Replace the screen and use ceramic paste as raw material to print a dielectric layer with a thickness of 50 μm on the basis of the first layer. Then put it into the oven and dry it at 80℃ for 10 min to obtain the second layer.

[0031] (4) Preparation of the third layer: Replace the screen and print the electrode pattern on the basis of the second layer using electrode silver paste as raw material. The printing thickness is 15μm. Then put it into the oven and dry it at 80℃ for 10min to obtain the third layer.

[0032] (5) Preparation of the fourth layer: Replace the screen and print a dielectric layer with a thickness of 50μm and holes on the basis of the third layer using ceramic paste as raw material. Then put it into the oven and dry it at 80℃ for 10min to obtain the fourth layer.

[0033] (6) Preparation of the fifth layer: Replace the screen, and on the basis of the fourth layer, use electrode silver paste as raw material to print to fill the holes and print an electrode pattern with a thickness of 15μm. Then put it into the oven and dry it at 80℃ for 10min to obtain the fifth layer.

[0034] (7) Repeat steps (5) and (6) once. After reaching the seventh layer, use ceramic paste as raw material to print a dielectric layer with a thickness of 50 μm on the seventh layer. Then put it into an oven and dry it at 80°C for 10 min. Cut it into granules, remove the glue at 350°C for 2 h, sinter at 900°C for 2 h, and finally roll the edges, silver the ends, sinter and electroplate to obtain the final product.

[0035] Example 2:

[0036] A method for fabricating a miniature LTCC filter includes the following steps:

[0037] (1) Preparation of ceramic paste with a solid content of 85wt%: 85 parts of LTCC microwave dielectric ceramic powder, 3 parts of polyacrylamide butyral resin, 3 parts of polyester, 4.5 parts of diethylene glycol monobutyl ether acetate and 4.5 parts of terpineol are mixed by weight and mixed evenly by three drums and centrifugal mixer to obtain the paste.

[0038] The LTCC microwave dielectric ceramic powder comprises the following components by weight: 54 parts SiO2, 43 parts Al2O3, 1 part B2O3, and 2 parts TiO2.

[0039] (2) Preparation of the first layer: Using release PET film as transfer film on printing equipment, electrode silver paste (manufacturer: NAMICS CORPORATION; model: 7396; solid content 85%) is used as raw material. A screen is placed on the transfer film to print the electrode pattern. The printing thickness is 15μm. After printing, it is placed in an oven and dried at 80℃ for 10min to complete the external circuit electrode and obtain the first layer.

[0040] (3) Preparation of the second layer: Replace the screen and use ceramic paste as raw material to print a dielectric layer with a thickness of 50 μm on the basis of the first layer. Then put it into the oven and dry it at 80℃ for 10 min to obtain the second layer.

[0041] (4) Preparation of the third layer: Replace the screen and print the electrode pattern on the basis of the second layer using electrode silver paste as raw material. The printing thickness is 15μm. Then put it into the oven and dry it at 80℃ for 10min to obtain the third layer.

[0042] (5) Preparation of the fourth layer: Replace the screen and print a dielectric layer with a thickness of 50μm and holes on the basis of the third layer using ceramic paste as raw material. Then put it into the oven and dry it at 80℃ for 10min to obtain the fourth layer.

[0043] (6) Preparation of the fifth layer: Replace the screen, and on the basis of the fourth layer, use electrode silver paste as raw material to print to fill the holes and print an electrode pattern with a thickness of 15μm. Then put it into the oven and dry it at 80℃ for 10min to obtain the fifth layer.

[0044] (7) Repeat steps (5) and (6) once. After reaching the seventh layer, use ceramic paste as raw material to print a dielectric layer with a thickness of 50 μm on the seventh layer. Then put it into an oven and dry it at 80°C for 10 min. Cut it into granules, remove the glue at 350°C for 2 h, sinter at 900°C for 2 h, and finally roll the edges, silver the ends, sinter and electroplate to obtain the final product.

[0045] Example 3:

[0046] A method for fabricating a miniature LTCC filter includes the following steps:

[0047] (1) Preparation of ceramic paste with a solid content of 92wt%: 92 parts of LTCC microwave dielectric ceramic powder, 3 parts of polyacrylamide butyral resin, 3 parts of polyester, 1 part of diethylene glycol monobutyl ether acetate and 1 part of terpineol are mixed by weight and mixed evenly by three drums and centrifugal mixer to obtain the paste.

[0048] The LTCC microwave dielectric ceramic powder comprises the following components by weight: 54 parts SiO2, 43 parts Al2O3, 1 part B2O3, and 2 parts TiO2.

[0049] (2) Preparation of the first layer: Using release PET film as transfer film on printing equipment, electrode silver paste (manufacturer: NAMICS CORPORATION; model: 7396; solid content 85%) is used as raw material. A screen is placed on the transfer film to print the electrode pattern. The printing thickness is 15μm. After printing, it is placed in an oven and dried at 80℃ for 10min to complete the external circuit electrode and obtain the first layer.

[0050] (3) Preparation of the second layer: Replace the screen and use ceramic paste as raw material to print a dielectric layer with a thickness of 50 μm on the basis of the first layer. Then put it into the oven and dry it at 80℃ for 10 min to obtain the second layer.

[0051] (4) Preparation of the third layer: Replace the screen and print the electrode pattern on the basis of the second layer using electrode silver paste as raw material. The printing thickness is 15μm. Then put it into the oven and dry it at 80℃ for 10min to obtain the third layer.

[0052] (5) Preparation of the fourth layer: Replace the screen and print a dielectric layer with a thickness of 50μm and holes on the basis of the third layer using ceramic paste as raw material. Then put it into the oven and dry it at 80℃ for 10min to obtain the fourth layer.

[0053] (6) Preparation of the fifth layer: Replace the screen, and on the basis of the fourth layer, use electrode silver paste as raw material to print to fill the holes and print an electrode pattern with a thickness of 15μm. Then put it into the oven and dry it at 80℃ for 10min to obtain the fifth layer.

[0054] (7) Repeat steps (5) and (6) once. After reaching the seventh layer, use ceramic paste as raw material to print a dielectric layer with a thickness of 50 μm on the seventh layer. Then put it into an oven and dry it at 80°C for 10 min. Cut it into granules, remove the glue at 350°C for 2 h, sinter at 900°C for 2 h, and finally roll the edges, silver the ends, sinter and electroplate to obtain the final product.

[0055] Comparative Example 1:

[0056] A method for fabricating a miniature LTCC filter includes the following steps:

[0057] (1) Using ethanol, toluene, polyether phosphate, polyvinyl butyral and diisobutyl phthalate as raw materials, the mixture was ball-milled and then vacuum defoamed to obtain a ceramic slurry with a solid content of 50wt%.

[0058] (2) Using the ceramic slurry obtained in step (1) as raw material, a LTCC green ceramic tape with a thickness of 50 μm is obtained after drying.

[0059] (3) Cut the LTCC green ceramic tape obtained in step (2) into pieces, drill holes with laser, inject electrode silver paste into the micropores to obtain the circuit pattern, and finally dry at 80°C for 10 min to obtain the green ceramic tape covered with metal electrodes.

[0060] (4) First, the four green ceramic strips covered with metal electrodes obtained in step (3) are subjected to stacking isostatic pressing, then cut into granules, then debinded at 350°C for 2 hours, sintered at 900°C for 2 hours, and finally rolled edges, silvered ends, sintered and electroplated to obtain the final product.

[0061] Comparative Example 2:

[0062] A method for fabricating a miniature LTCC filter includes the following steps:

[0063] (1) Preparation of ceramic paste with a solid content of 60wt%: 60 parts of LTCC microwave dielectric ceramic powder, 3 parts of polyacrylamide butyral resin, 3 parts of polyester, 17 parts of diethylene glycol monobutyl ether acetate and 17 parts of terpineol are mixed by weight and mixed evenly by three drums and centrifugal mixer to obtain the paste.

[0064] The LTCC microwave dielectric ceramic powder comprises the following components by weight: 54 parts SiO2, 43 parts Al2O3, 1 part B2O3, and 2 parts TiO2.

[0065] (2) Preparation of the first layer: Using release PET film as transfer film on printing equipment, electrode silver paste (manufacturer: NAMICS CORPORATION; model: 7396; solid content 85%) is used as raw material. A screen is placed on the transfer film to print the electrode pattern. The printing thickness is 15μm. After printing, it is placed in an oven and dried at 80℃ for 10min to complete the external circuit electrode and obtain the first layer.

[0066] (3) Preparation of the second layer: Replace the screen and use ceramic paste as raw material to print a dielectric layer with a thickness of 50 μm on the basis of the first layer. Then put it into the oven and dry it at 80℃ for 10 min to obtain the second layer.

[0067] (4) Preparation of the third layer: Replace the screen and print the electrode pattern on the basis of the second layer using electrode silver paste as raw material. The printing thickness is 15μm. Then put it into the oven and dry it at 80℃ for 10min to obtain the third layer.

[0068] (5) Preparation of the fourth layer: Replace the screen and print a dielectric layer with a thickness of 50μm and holes on the basis of the third layer using ceramic paste as raw material. Then put it into the oven and dry it at 80℃ for 10min to obtain the fourth layer.

[0069] (6) Preparation of the fifth layer: Replace the screen, and on the basis of the fourth layer, use electrode silver paste as raw material to print to fill the holes and print an electrode pattern with a thickness of 15μm. Then put it into the oven and dry it at 80℃ for 10min to obtain the fifth layer.

[0070] (7) Repeat steps (5) and (6) once. After reaching the seventh layer, use ceramic paste as raw material to print a dielectric layer with a thickness of 50 μm on the seventh layer. Then put it into an oven and dry it at 80°C for 10 min. Cut it into granules, remove the glue at 350°C for 2 h, sinter at 900°C for 2 h, and finally roll the edges, silver the ends, sinter and electroplate to obtain the final product.

[0071] Experimental example:

[0072] The miniature LTCC filters prepared in Examples 1-3 and Comparative Examples 1-2 were characterized. The four sides of the green blank before debinding and sintering were cut off using a cutting machine. The cut four sides were placed under a video microscope for inspection and measurement. The widest point A and the narrowest point B were measured, and the stack offset = (AB) / 2 was calculated. The frequency offset caused by the stack offset was detected using a Rhodes network analyzer.

[0073] The experimental results are shown in Table 1.

[0074] Table 1 Performance Characterization

[0075]

[0076] As shown in Table 1, the miniature LTCC filter prepared by overlaying ceramic paste and silver paste in this embodiment of the invention can effectively avoid stack-up misalignment and reduce frequency deviation caused by stack-up misalignment. Furthermore, no cracking occurs during sintering. In contrast, the miniature LTCC filters prepared using traditional methods or low-solids-content ceramic paste (60 wt%) in Comparative Examples 1-2 exhibit significantly higher stack-up misalignment than those in this embodiment. In Comparative Example 2, the low solids content of the ceramic paste leads to large shrinkage variations in the dielectric layer during sintering, resulting in post-sintering misalignment and thickness differences, thus degrading performance. This invention's preparation method not only reduces the preparation process compared to traditional methods but also eliminates the need for high-precision instruments, effectively avoiding the problems of electrical differences caused by variations between multiple process steps in the fabrication of miniature LTCC filters.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a miniature LTCC filter, characterized in that, Includes the following steps: First, electrode pattern is printed on a transfer film using electrode silver paste as raw material. Then, ceramic paste and electrode silver paste are used alternately as raw materials to print and dry the dielectric layer and electrode pattern to obtain a blank. Then, the blank is dried, cut, debinded and sintered, and finally processed by post-processing. The fourth layer is a dielectric layer with holes, and the fifth layer is an electrode pattern that fills or prints the holes in the fourth layer. The preparation of the fourth and fifth layers is repeated several times until the target number of layers is reached. Then, the top layer is prepared using ceramic paste as the raw material. The target number of layers is 5+2n, where n=0~100. The ceramic paste is prepared by mixing the following components in parts by weight: 75-92 parts of LTCC microwave dielectric ceramic powder, 1-5 parts of polyacrylamide butyral resin, 1-5 parts of polyester, 5-15 parts of diethylene glycol monobutyl ether acetate and 5-15 parts of terpineol. The LTCC microwave dielectric ceramic powder comprises the following components by weight: 50-60 parts SiO2, 40-50 parts Al2O3, 0.5-2 parts B2O3, and 1-3 parts TiO2.

2. The method for fabricating a miniature LTCC filter according to claim 1, characterized in that, The transfer film includes OPP film or release PET film.

3. The method for fabricating a miniature LTCC filter according to claim 1, characterized in that, The solid content of the electrode silver paste is 75~92wt%.

4. The method for fabricating a miniature LTCC filter according to claim 1, characterized in that, The solid content of the ceramic paste is 75-92 wt%, and the viscosity of the ceramic paste is 100,000-600,000 Cp.

5. The method for fabricating a miniature LTCC filter according to claim 1, characterized in that, The drying temperature for each layer after printing is 40~100℃, and the time is 5~15 minutes.

6. The method for fabricating a miniature LTCC filter according to claim 1, characterized in that, Each layer has a thickness of 5~120 μm.

7. The method for fabricating a miniature LTCC filter according to claim 1, characterized in that, The temperature for debinding is 250~450℃ and the time is 1~5 h. The temperature for sintering is 850~950℃ and the time is 1~5 h.

8. The method for fabricating a miniature LTCC filter according to claim 1, characterized in that, The post-processing includes edge rolling, silver finishing, heat treatment, and electroplating.

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