EP-4741365-A1 - METHOD FOR PRODUCING CERAMIC SUBSTRATE

EP4741365A1EP 4741365 A1EP4741365 A1EP 4741365A1EP-4741365-A1

Abstract

There is provided a method for producing a ceramic substrate that can appropriately set the amount of a release agent adhered to a ceramic green sheet. According to an embodiment of the invention, a method for producing a ceramic substrate includes an adhesion process of adhering a release agent to two surfaces of a ceramic green sheet having a first surface and a second surface, and a sintering process of overlaying and sintering multiple ceramic green sheets to which the release agent is adhered. In the ceramic green sheet after the adhesion process, an adhesion ratio of the release agent on the first surface and an adhesion ratio of the release agent on the second surface each are not less than 5% and not more than 30%. A difference between the adhesion ratio of the release agent on the first surface and the adhesion ratio of the release agent on the second surface is not more than 20%.

Inventors

AKIYA, Suguru
ICHIKAWA, HIROSHI
AKIMOTO, TOSHIYA
ODA, TATSUYA
KONDO, HIROYASU

Assignees

Niterra Materials Co., Ltd.

Dates

Publication Date: 20260513
Application Date: 20240628

Claims (7)

A method for producing a ceramic substrate, the method comprising: an adhesion process of adhering a release agent to two surfaces of a ceramic green sheet, the ceramic green sheet having a first surface and a second surface; and a sintering process of overlaying and sintering a plurality of the ceramic green sheets to which the release agent is adhered, in the ceramic green sheet after the adhesion process, an adhesion ratio of the release agent on the first surface and an adhesion ratio of the release agent on the second surface each being not less than 5% and not more than 30%, a difference between the adhesion ratio of the release agent on the first surface and the adhesion ratio of the release agent on the second surface being not more than 20%.
The method for producing the ceramic substrate according to claim 1, wherein in the adhesion process, the release agent is adhered to the second surface within 30 minutes after the release agent is adhered to the first surface.
The method for producing the ceramic substrate according to claim 2, wherein the adhesion ratio of the release agent on the first surface is greater than the adhesion ratio of the release agent on the second surface.
The method for producing the ceramic substrate according to claim 1 or claim 2, wherein when the first surface and the second surface each are uniformly divided into four areas after the adhesion process, and when adhesion ratios of the release agent in each of the areas are measured, a difference between a maximum of the adhesion ratios and a minimum of the adhesion ratios of the first surface is not more than 20%, and a difference between a maximum of the adhesion ratios and a minimum of the adhesion ratios of the second surface is not more than 20%.
The method for producing the ceramic substrate according to claim 1 or claim 2, further comprising: a cutting process of cutting the ceramic green sheet after the adhesion process, the sintering process including overlaying the cut ceramic green sheets.
The method for producing the ceramic substrate according to claim 1 or claim 2, wherein the ceramic green sheet includes one of silicon nitride, aluminum nitride, or aluminum oxide.
The method for producing the ceramic substrate according to claim 1 or claim 2, wherein a thickness of the ceramic green sheet is not more than 1.0 mm.

Description

[Technical Field] Embodiments relate to a method for producing a ceramic substrate. [Background Art] With the development in recent years of semiconductor elements requiring large currents such as power electronics, next-generation power semiconductors, and the like, the demand for ceramic substrates providing both heat dissipation and electrical insulation has been increasing year by year. In particular, as the heat generation of elements increases with downsizing and higher performance, there is a tendency to reduce the thickness of ceramic substrates to dissipate heat efficiently. On the other hand, to lower the production cost of ceramic substrates, technology has been discussed in which ceramic substrates are produced with larger shapes (Patent Literature 1). Among ceramic substrates, silicon nitride substrates have high strength, high toughness, and good heat dissipation. According to Patent Literature 1, a silicon nitride substrate with a size of 220 mm×220 mm×0.32 mm has been obtained. As a method for producing a ceramic substrate, technology has been discussed in which multiple green sheets are stacked with a separating material interposed (Patent Literature 2). The stacked green sheets are separated from each other after sintering. Multiple ceramic substrates are produced thereby. According to Patent Literature 2, boron nitride powder is coated as a separating material on one surface or two surfaces of the cut green sheet. Subsequently, the stacked multiple green sheets are sintered and then separated to obtain multiple silicon nitride sintered bodies. A method of coating a release agent onto a ceramic green sheet with a roll coater also has been discussed (Patent Literature 3). According to Patent Literature 3, multiple ceramic green sheets are stacked, the upper surface and lower surface of the stacked body each are pressed with a setter made of boron nitride (BN), followed by sintering to obtain multiple ceramic sintered bodies. [Prior Art Documents] [Patent Literature] Patent Literature 1: Japanese Patent No. 6399252Patent Literature 2: Japanese Patent No. 5339214Patent Literature 3: Japanese Patent No. 3369819 [Summary of Invention] [Problem to be Solved by the Invention] A green sheet of a ceramic substrate is produced by mixing an organic binder with a ceramic powder and by drying the ceramic powder and the organic binder. The green sheet does not have the strength of a resin film or a metal foil, and is easily damaged by tension. On the other hand, ceramic substrates tend to become thinner as products become smaller. Also, to reduce the cost by producing efficiently, there is a tendency to increase the size of the ceramic green sheet. It is desirable to appropriately control the amount of the release agent adhered to the ceramic green sheet due to the effects of the amount on the quality and productivity of the ceramic substrate. For example, if the amount of the release agent is low, it becomes difficult to separate the sintered ceramic substrates from each other. Therefore, it takes time and effort to separate the ceramic substrates from each other. If the ceramic substrates cannot be separated, the ceramic substrates become defective. If much of the release agent is adhered, the separation is easier, but the cost of the release agent is increased. Also, if the adhesion amount is uneven, waviness of the ceramic substrate becomes large, which causes defects. Therefore, in the production of a ceramic substrate, it is desirable to appropriately control the amount of the release agent adhered to the ceramic green sheet. [Means for Solving the Problem] A method for producing a ceramic substrate according to an embodiment includes an adhesion process and a sintering process. The adhesion process includes adhering a release agent to two surfaces of a ceramic green sheet having a first surface and a second surface. The sintering process includes overlaying and sintering multiple ceramic green sheets to which the release agent is adhered. In the ceramic green sheet after the adhesion process, an adhesion ratio of the release agent on the first surface and an adhesion ratio of the release agent on the second surface each are not less than 5% and not more than 30%. A difference between the adhesion ratio of the release agent on the first surface and the adhesion ratio of the release agent on the second surface is not more than 20%. [Brief Description of Drawings] [FIG. 1] FIG. 1 is a perspective view showing an example of a ceramic green sheet according to an embodiment.[FIG. 2] FIG. 2 is a cross-sectional view showing an example of the ceramic green sheet according to the embodiment.[FIG. 3] FIG. 3 is a flowchart showing a method for producing a ceramic substrate according to an embodiment.[FIG. 4] FIG. 4 is a cross-sectional view showing an example of the production process of the ceramic substrate according to the embodiment.[FIG. 5] FIG. 5 is a cross-sectional view showing an example of a produ