Via hole metallization sintering process for aluminum nitride heater

Abstract

The invention relates to a via hole metallization sintering process for an aluminum nitride heater. The process is characterized by comprising the following specific sintering processes: S1, sintering the aluminum nitride heater for the first time; s2, hole filling and drying of tungsten or molybdenum metallization slurry; s3, sintering the aluminum nitride heater for the second time; according to the method, after the green body is punched, glue discharging and sintering are directly carried out, the sintering temperature is set to be about 1700 DEG C, after sintering is carried out at the temperature section, a biscuit of the heater is formed, and the biscuit has certain strength which is obviously higher than that of the green body or after glue discharging and also has enough air holes so that metallization slurry can permeate conveniently; carrying out hole filling and drying on tungsten or molybdenum metallization slurry on the basis of the biscuit; after drying, secondary sintering is carried out, and the sintering temperature is selected from normal sintering; and under the working procedure, cracks of the tungsten metallization layer or defects of the aluminum nitride layer in molybdenum metallization can be improved and even eliminated.

Description

Technical Field

[0001] This invention relates to the field of electronic ceramics technology, and in particular to a through-hole metallization sintering process for aluminum nitride heaters. Background Technology

[0002] Semiconductor chip packaging and testing requires rapid heating and precise temperature control. Aluminum nitride ceramic materials possess high thermal conductivity and good mechanical strength, making them suitable for chip packaging and testing applications. Currently, aluminum nitride heaters produced using existing technology consist of a heating substrate formed by casting aluminum nitride powder and yttrium oxide powder in a specific ratio. This substrate carries the heating circuitry and connects wires. Aluminum nitride ceramic serves as both an insulating and thermally conductive substrate material, and heating is achieved by printing tungsten-molybdenum paste inside the substrate. Due to the excellent thermal conductivity and low coefficient of thermal expansion of the aluminum nitride substrate, it is suitable for high-power-density applications.

[0003] The applicant filed patent CN114710847 A a few years ago, entitled "Electronic Ceramic Heater for Semiconductor Chip Packaging and Testing and its Preparation Method," which described the structure and basic process of an aluminum nitride heater. In 2023, they also submitted "An Aluminum Nitride Heater with Low Resistance Temperature Coefficient and its Preparation Method" (CN202310564248.X), describing the materials and process of a heater with a low resistance temperature coefficient. The heater has lead holes or thermocouple holes, used for connecting an external heating power supply or for thermocouple temperature measurement and feedback temperature control, respectively. The metallization paste for these vias, such as lead holes and thermocouple holes, generally uses a paste similar to that used for the heating circuit, or a paste specially formulated with tungsten alloy or molybdenum alloy. After drilling, the holes are metallized first, and then debonded and sintered together with the heater as a whole. In other words, the sintering of these via metallized vias is generally completed using the same debonding and sintering process as the heater product. The physical location of the metallization paste on the surface of the hole is different from that of the heated paste sandwiched between the ceramics, and its sintering behavior is also different. The corresponding sintering process is not suitable for the metallization paste, as it is easy to generate defects in the hole. These defects appear on the metallization layer itself or on the ceramic layer connected to it, thereby causing problems such as reduced insulation and aging failure of the product.

[0004] CN114710847A or CN202310564248.X clearly describe the production process of aluminum nitride ceramic heaters based on tape casting technology, which basically includes slurry preparation, aluminum nitride sheet tape casting, cutting, screen printing (printing conductive lines), isostatic pressing, cutting, drilling, via metallization, debinding and sintering, brazing and subsequent processing. This invention focuses on the via metallization and subsequent sintering process. After drilling is completed on the green body, the prepared metallization slurry (tungsten or molybdenum metallization slurry) is directly poured into the holes and dried at a certain temperature. After the solvent dries, the remaining slurry adheres to the surface of the holes. Then, this dried heater green body undergoes debinding and sintering, with the sintering temperature generally above 1800°C. Because the sintering temperature of tungsten or molybdenum differs significantly from that of aluminum nitride (1800°C); if tungsten metallization paste is used, due to its high sintering temperature (generally 1900-2200°C), direct sintering with aluminum nitride would result in cracks appearing directly within the metallization layer. Figure 2 Molybdenum has a relatively low sintering temperature (it can be densified at 1400-1500°C), and if it is sintered directly with aluminum nitride, cracks will appear directly in the aluminum nitride near the metallization point. Figure 3 These factors all affect the final performance of aluminum nitride heaters. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a through-hole metallization sintering process for aluminum nitride heaters. In view of the problem of through-hole metallization defects, a two-step sintering process is adopted to coordinate the sintering performance differences between ceramic and through-hole metal, improve the metal or ceramic defects in the through-hole after sintering, and thus improve the performance of the heater product.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a metallization sintering process for through-holes in an aluminum nitride heater, the innovation of which lies in the following specific sintering process: S1: First sintering of aluminum nitride heater: After the green blank is punched, the aluminum nitride heater is directly sintered by debinding, and the sintering temperature is 1650℃-1730℃, and the time is 2-4h. S2: Filling and drying of tungsten or molybdenum metallization slurry: After the first sintering of the aluminum nitride heater is completed, the prepared tungsten or molybdenum slurry needs to be diluted with an organic solvent; then it is poured into the holes of the aluminum nitride heater and dried. S3: Second sintering of aluminum nitride heater: After the completion of S1 sintering, the second sintering is carried out at a temperature of 1830℃-1850℃ for 2-3 hours.

[0007] Furthermore, in step S1, after drilling is completed, the adhesive is removed in an N2 atmosphere according to the general aluminum nitride adhesive removal process to ensure that the heater is free of defects after adhesive removal. Then, sintering is carried out in an N2-H2 mixed atmosphere, with the temperature increased to 1650℃-1730℃ at 3°C / min and held for 2-4 hours. Then, the heater is cooled in the furnace to obtain the blank of the heater.

[0008] Furthermore, sintering is carried out in the N2-H2 mixed atmosphere in S2, with the temperature increased to 1830℃-1850℃ at 3°C / min, held for 2-3 hours, and then cooled in the furnace to finally obtain a metallized heater product with no obvious defects in the power hole.

[0009] The advantages of this invention are: 1) In this invention, after drilling holes in the green blank, the binder is removed and sintering is carried out directly. The sintering temperature is set at about 1700°C. After sintering at this temperature, a green blank for the heater is formed, which has a certain strength, which is significantly higher than that of the green blank or after binder removal. It also has enough pores to facilitate the penetration of metallization paste. On the basis of the green blank, tungsten or molybdenum metallization paste is poured into the holes and dried. After drying, a second sintering is carried out. The sintering temperature can be selected from normal sintering conditions (such as 1835 or 1840°C). In this process, the cracks in the tungsten metallization layer itself or the defects in the aluminum nitride layer in the molybdenum metallization can be improved or even eliminated. Attached Figure Description

[0010] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0011] Figure 1 This is a flow chart of a through-hole metallization sintering process for an aluminum nitride heater according to the present invention.

[0012] Figure 2 Figure 3 This is a defect diagram of a conventional aluminum nitride heater after a single sintering process. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0014] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0015] like Figure 1 The above describes a through-hole metallization sintering process for an aluminum nitride heater. The specific sintering process is as follows: S1: First sintering of aluminum nitride heater: After the green blank is punched, the aluminum nitride heater is directly sintered by debinding, and the sintering temperature is 1650℃-1730℃, and the time is 2-4h. S2: Filling and drying of tungsten or molybdenum metallization slurry: After the first sintering of the aluminum nitride heater is completed, the prepared tungsten or molybdenum slurry needs to be diluted with an organic solvent; then it is poured into the holes of the aluminum nitride heater and dried. S3: Second sintering of aluminum nitride heater: After the completion of S1 sintering, the second sintering is carried out at a temperature of 1830℃-1850℃ for 2-3 hours.

[0016] In S1, after drilling, the adhesive is removed in an N2 atmosphere according to the general aluminum nitride adhesive removal process to ensure that the heater is free of defects after adhesive removal. Then, sintering is carried out in a N2-H2 mixed atmosphere, with the temperature increased to 1650℃-1730℃ at 3°C / min and held for 2-4 hours. Then, the heater is cooled in the furnace to obtain the blank of the heater.

[0017] Sintering is carried out in a mixed atmosphere of S2, N2-H2, with the temperature increased to 1830℃-1850℃ at 3°C / min, held for 2-3 hours, and then cooled in the furnace to obtain a metallized heater product with no obvious defects in the power hole.

[0018] Example 1: For a certain 40*40mm heater product, after the heating wire printing and isostatic pressing, holes are drilled at two terminals of the heating wire to allow for external power supply. These two power supply holes are φ1.5*2.2mm (2.2mm deep), are straight holes, and the bottom of the holes passes through the printed terminals on the heating wire. After drilling, the aluminum nitride is de-adsorbed in a nitrogen atmosphere according to a standard aluminum nitride de-adsorption process to ensure the heater is defect-free. Then, sintering is performed in a N2-H2 (volume ratio 1:1) mixed atmosphere, with the temperature increased to 1700 degrees Celsius at 3°C / min, held for 2 hours, and then furnace cooled to obtain the heater blank. Based on the raw blank, tungsten slurry is metallized. The tungsten heating circuit slurry is diluted with 50% by mass of an organic solvent (such as acetone or isopropanol) for metallizing the power holes. After the metallized slurry fills the power holes, it is dried (24 hours at room temperature or 3 hours at 40°C). After drying, it is sintered a second time in a N2-H2 (1:1 volume ratio) mixed atmosphere, heated to 1840°C at 3°C / min, held for 2 hours, and then furnace cooled. Finally, a power hole metallized heater product with no obvious defects is obtained.

[0019] Example 2: For a certain 20*50mm heater product, after the heating wire printing and isostatic pressing, holes are drilled at two terminals of the heating wire to allow for external power supply. These two power supply holes are φ1.5*2.0mm (2.0mm deep), are straight holes, and the bottom of the holes passes through the printed terminals on the heating wire. After drilling, the aluminum nitride is de-adsorbed in a nitrogen atmosphere according to a standard aluminum nitride de-adsorption process to ensure the heater is defect-free. Then, sintering is performed in a N2-H2 (volume ratio 1:1) mixed atmosphere, with the temperature increased to 1720 degrees Celsius at 3°C / min, held for 2 hours, and then furnace cooled to obtain the heater blank. Based on the raw blank, a separately prepared molybdenum slurry is used for metallization. After the metallized slurry fills the power hole, it is dried (30 hours at room temperature or 3 hours at 45°C). After drying, it is sintered a second time in a N2-H2 (volume ratio 1:1) mixed atmosphere, heated to 1835°C at 3°C / min, held at that temperature for 3 hours, and then cooled in a furnace. Finally, a metallized heater product with no obvious defects in the power hole is obtained.

[0020] Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A through-hole metallization sintering process for an aluminum nitride heater, characterized in that: The specific sintering process is as follows: S1: First sintering of aluminum nitride heater: After the green blank is punched, the aluminum nitride heater is directly subjected to debinding sintering, and the sintering temperature is 1650℃-1730℃, and the time is 2-4h. S2: Filling and drying of tungsten or molybdenum metallization slurry: After the first sintering of the aluminum nitride heater is completed, the prepared tungsten or molybdenum slurry needs to be diluted with an organic solvent; then it is poured into the holes of the aluminum nitride heater and dried. S3: Second sintering of aluminum nitride heater: After the completion of S1 sintering, the second sintering is carried out at a temperature of 1830℃-1850℃ for 2-3 hours.

2. The through-hole metallization sintering process for an aluminum nitride heater according to claim 1, characterized in that: In step S1, after drilling is completed, the adhesive is removed in an N2 atmosphere according to the general aluminum nitride adhesive removal process to ensure that the heater is free of defects after adhesive removal. Then, sintering is carried out in an N2-H2 mixed atmosphere, with the temperature increased to 1650℃-1730℃ at 3°C / min and held for 2-4 hours. Then, the heater is cooled in the furnace to obtain the blank of the heater.

3. The through-hole metallization sintering process for an aluminum nitride heater according to claim 1, characterized in that: Sintering is carried out in the N2-H2 mixed atmosphere of S2, with the temperature increased to 1830℃-1850℃ at 3°C / min, held for 2-3 hours, and then cooled in the furnace to finally obtain a metallized heater product with no obvious defects in the power hole.

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