Process for improving high-temperature sintering warping of ceramic substrate

Abstract

The invention provides a process for improving high-temperature sintering warpage of a ceramic substrate, which adopts a co-shrinkage soaring method for the first time, and is technically characterized in that before a substrate is sintered, a green body which is made of the same material as a sintered product and is slightly thicker than a green body of the sintered product is adopted as a cushion block to be respectively placed on the periphery of a green body of the substrate, and a cover plate covers the green body of the substrate; and finally sintering at high temperature. Due to the fact that the cushion blocks are shrunk with the same shrinking percentage as the product in the sintering process, the thickness of the surrounding cushion blocks is larger than that of the product all the time in the sintering process, the product can be located in a small limiting space all the time, and the warping problem generated in the sintering process of the ceramic substrate can be solved. The preparation process is simple and easy to implement, and has wide application prospects in the fields of electronic packaging and precision part manufacturing.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic materials, and is a process for improving the warping of a ceramic substrate during high-temperature sintering. Background Art

[0002] Electronic ceramic substrates are widely used in the electronics industry, communications, industrial lasers, consumer electronics, automotive electronics and other industries due to their excellent physical and chemical properties. With the development of high-density integration of electronic devices, electronic ceramic substrates are also developing in the direction of being smaller and thinner, and thinner ceramic substrates are more prone to warping problems, which is also a common problem in the current production of ceramic substrates. During sintering, the air in the green body is continuously discharged at high temperatures, so volume shrinkage is inevitable. Uneven shrinkage of ceramics will lead to internal stress concentration, warping and other problems, thereby affecting the physical and chemical properties of ceramics. Therefore, reducing shrinkage and improving warping during the manufacturing process of ceramic components is particularly important for improving dimensional accuracy and the uniformity of the microstructure and performance of complex-shaped components. Summary of the invention

[0003] The object of the present invention is to provide a process for improving the warpage of a ceramic substrate during high temperature sintering.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a process for improving the warpage of a ceramic substrate during high temperature sintering, comprising the following steps:

[0005] S1, mixing ceramic powder with sintering aid, colorant, organic solvent and dispersant in a certain proportion, and preparing casting slurry after ball milling and degassing;

[0006] S2, tape casting method: the slurry is tape cast into a green embryo, and the layers are stacked to different thicknesses, wherein the thickness of the cushion green embryo is slightly greater than the thickness of the product green embryo, and then isostatically pressed and cut;

[0007] S3, placing the green embryo on the firing plate, placing a green embryo with a thickness slightly larger than the green embryo around the product, and then adding a cover plate, and using this co-shrinkage vacancy method to perform debinding sintering;

[0008] S4. Transfer the debinding products directly to a high-temperature sintering furnace or use a debinding and sintering integrated furnace to sinter them into porcelain at high temperature.

[0009] S5. Take out the product after the equipment cools down.

[0010] As a preferred solution, the ceramic substrate may be a black alumina ceramic substrate.

[0011] As a preferred solution, the mass percentage of Al2O3 powder in the black alumina slurry is 45-55%; the sintering aid is SiO2, which is 1.5%-4% by mass. The colorant is Co2O3, which is 2.5%-6% by mass. The organic solvent is anhydrous ethanol, which is 15%-30% by mass. The dispersant is polyisobutylene, which is 6%-10% by mass.

[0012] As a preferred solution, the ball milling speed is 200R, and the ball milling time is 12 hours;

[0013] As a preferred solution, the thickness of the laminated embryo is 0.43 mm.

[0014] As a preferred solution, the isostatic pressing pressure is 8000 psi and maintained for 5 min to obtain a denser ceramic green body.

[0015] As a preferred solution, a co-shrinkage vacant sintering method is adopted, and a 0.4 mm thick black alumina product embryo is placed on a corundum mullite support plate, and four black alumina embryo pads of the same thickness (greater than 0.43 mm) are placed around the product embryo, and a corundum mullite plate is covered on top.

[0016] As a preferred solution, the black alumina debinding process raises the furnace temperature to 1000-1300°C at a rate of 2°C / min:

[0017] As a preferred solution, the black alumina sintering atmosphere adopts a mixture of nitrogen and wet hydrogen, and above this temperature, a mixture of nitrogen and dry hydrogen is adopted, and the hydrogen ratio is 10%-50%.

[0018] As a preferred solution, the high temperature sintering temperature is 1400°C-1600°C at a speed of 3°C / min.

[0019] The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least:

[0020] 1) The present invention adopts the air-co-shrinkage sintering method to effectively limit the shrinkage of the ceramic substrate in the plane. Through this process, the sintering warpage of the plane size of the substrate can be controlled to 0.7‰-0.8‰. Compared with the traditional free flat method, it has good flatness and low warpage. Compared with the pressure sintering, the sample is not easy to break and produce pits due to excessive gravity. Compared with the traditional air-co-shrinkage sintering method, the air-co-shrinkage sintering method can further limit the warpage and obtain a flatter product.

[0021] 2) The present invention uses green embryo pads of different thicknesses for sintering. It can be seen that as the thickness of the green embryo pad increases, the warpage increases. When the thickness is 0.43 mm, the shrinkage rate and the warpage are basically stable, reaching a very small warpage of 0.7‰-0.8‰.

[0022] 3) The use of the air co-shrinkage sintering method can complete the production of substrates with very small warpage, without the need to purchase special equipment or change the material system. The process is simple, low-cost and easy to apply. Through this process method, special samples such as low-warpage and high-flatness substrates can be processed and manufactured. In the future, this process will play a greater role in special structural applications such as high-density MCM-C, MCM-C / D, and LTCC microsystems. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] Figure 1 It is a technical diagram of the traditional free-laying method, weight-pressing method, air-lifting method and air-lifting co-contraction method;

[0025] Figure 2 This is a picture of the sample after high-temperature sintering using the air co-shrinkage method in Example 1;

[0026] Figure 3 This is a picture of the sample after high temperature sintering using the traditional free-laying method in Example 3;

[0027] Figure 4 The warpage test results of the products sintered in Example 1, Example 2 and Comparative Example 3 are shown; DETAILED DESCRIPTION

[0028] To make the purpose, technical solution and advantages of the present application clearer, the following will further describe the implementation of the present application in detail with reference to the accompanying drawings. In the embodiment, black alumina is used as an example, and the method can also be applied to other high-temperature sintered ceramic substrates.

[0029] Example 1

[0030] 1. Select black alumina powder, of which Al2O3 accounts for 45%, mix it with SiO2, Co2O3, polyisobutylene and anhydrous ethanol, and mix it evenly in a ball mill for 12 hours at a speed of 200r / min to obtain a mixed slurry.

[0031] 2. The slurry is cast into a green embryo. The green embryo stacking thickness of the product is 0.4mm. The green embryo pads are stacked to different thicknesses, namely 0.43mm, 0.53mm, 0.57mm, and 0.65mm, and then statically pressed and cut.

[0032] 3. Use the co-shrinkage vacant sintering method to place several 0.4mm thick black alumina green embryos on a steel and mullite support plate. Place 4 black alumina green embryo pads of the same thickness and slightly thicker than the product around each green embryo. For comparative experiments, place pads with thicknesses of 0.43mm, 0.53mm, 0.57mm, and 0.65mm around different products. Cover the top with a corundum mullite plate. Place the product in an atmosphere debinding sintering integrated furnace, and continue to raise the furnace temperature to 1000-1300℃ at a rate of 2℃ / min for debinding. Below this temperature, the atmosphere condition uses a mixture of nitrogen and wet hydrogen, and above this temperature, a mixture of nitrogen and dry hydrogen, with a hydrogen ratio of 10% to 50%.

[0033] 4. Continue to raise the furnace temperature to 1400℃~1600℃ at a rate of 5℃ / min and sinter into porcelain at high temperature.

[0034] 5. After the equipment has cooled down, take out the product for testing.

[0035] Example 2

[0036] 1. The slurry raw materials are the same as those in Example 1, but the proportions are different, wherein Al2O3 accounts for 55% (100.2 g) and is mixed with SiO2, Co2O3, polyisobutylene and anhydrous ethanol, and the speed is 200 r / min, and the ball mill is used for 12 hours to prepare a slurry;

[0037] 2. The slurry is cast into a green embryo. The green embryo stacking thickness of the product is 0.4mm. The pad green embryo is stacked to different thicknesses of 0.43mm, 0.53mm, 0.57mm, and 0.65mm, and then isostatically pressed and cut.

[0038] 3. Place several pieces of 0.4mm thick black alumina green embryos on the corundum mullite support plate, and place 4 black alumina green embryo pads of the same thickness and slightly thicker than the product around each green embryo. In order to conduct comparative experiments, pads with thicknesses of 0.43mm, 0.53mm, 0.57mm, and 0.65mm are placed around different products. Cover the top with a corundum mullite plate. Place the product in an atmosphere debinding and sintering integrated furnace, and continue to raise the furnace temperature to 1000-1300℃ at a rate of 2℃ / min for debinding. Below this temperature, the atmosphere condition uses a mixture of nitrogen and wet hydrogen, and above this temperature, a mixture of nitrogen and dry hydrogen is used, and the hydrogen ratio is 10%-50%.

[0039] 4. Continue to raise the furnace temperature to 1400℃~1600℃ at a rate of 5℃ / min and sinter into porcelain at high temperature.

[0040] 5. After the equipment has cooled down, take out the product for testing.

[0041] Comparative Example 3

[0042] 1. Select black alumina powder, Al2O3 accounts for 45%, and mix with SiO2, Co2O3,

[0043] Isobutylene and anhydrous ethanol were mixed, and the mixture was evenly mixed by ball milling in a ball mill at a speed of 200 r / min to obtain a mixed slurry.

[0044] 2. Cast the slurry into a green embryo, the product layer thickness is 0.4mm

[0045] 3. Use the free horizontal sintering method to place the black alumina product embryos on the corundum mullite support plate. Place the product in the atmosphere debinding sintering integrated furnace, and continue to increase the furnace temperature to 1000-1300℃ at a rate of 2℃ / min for debinding. Below this temperature, the atmosphere condition uses a mixture of nitrogen and wet hydrogen, and above this temperature, a mixture of nitrogen and dry hydrogen is used, and the hydrogen ratio is 10%-50%.

[0046] 4. Continue to raise the furnace temperature to 1400℃~1600℃ at a rate of 5℃ / min and sinter into porcelain at high temperature.

[0047] 5. After the equipment has cooled down, take out the sintered product.

[0048] Test Results

[0049] Example 1 Product pictures are as attached Figure 2 , Comparative Example 3 sintered product as shown in the attached Figure 3 It can be seen that compared with the traditional free-laying method, the air-co-shrinkage sintering method can obtain a flat product with almost no warping. Figure 4 From the product warpage test data of Example 1, Example 2 and Comparative Example 3, it can be seen that compared with the traditional free-laying method, the co-shrinkage air sintering method can greatly improve the flatness of the product, and under the appropriate pad thickness, a very small warpage can be achieved.

Claims

1. A process for improving the warpage of a ceramic substrate during high temperature sintering, characterized in that: The method comprises: S1, mixing ceramic powder with sintering aid, colorant, organic solvent and dispersant in a certain proportion, and preparing casting slurry after ball milling and degassing; S2, tape casting method: the slurry is tape cast into a green embryo, and the layers are stacked to different thicknesses, wherein the thickness of the cushion green embryo is slightly greater than the thickness of the product green embryo, and then isostatically pressed and cut; S3, placing the green embryo on the firing plate, placing a green embryo with a thickness slightly larger than the green embryo around the product, and then adding a cover plate, and using this co-shrinkage vacancy method to perform debinding sintering; S4. Transfer the debinding products directly to a high-temperature sintering furnace or use a debinding and sintering integrated furnace to sinter them into porcelain at high temperature. S5. Take out the product after the equipment cools down.

2. The process for improving the warpage of ceramic substrate during high temperature sintering according to claim 1, characterized in that: The thickness of the green spacer after lamination described in S2 is greater than the thickness of the product. The specific thickness difference is determined by the shrinkage rate of the product during the sintering process and the sintering effect.

3. The process for improving the warpage of ceramic substrate during high temperature sintering according to claim 1, characterized in that: The spacers placed in S3 need to be evenly distributed around the product embryos, and the number of spacer embryos placed around each product is 4.

4. The process for improving the warpage of ceramic substrate during high temperature sintering according to claim 1, characterized in that: The cover plate and the support plate described in S3 are made of corundum mullite plate to ensure that they are flat and not warped, and do not deform at high temperatures.

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