JP7232676B2 - ceramic substrate - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate, and more specifically to a ceramic substrate on which circuit elements forming at least part of a circuit are mounted.

As an electronic component using such a ceramic substrate, there is known a chip resistor in which the above circuit elements such as electrodes and resistors are mounted on a ceramic substrate. As described in Patent Document 1 below, electronic components such as chip resistors are manufactured by printing circuit elements such as electrodes and resistors on the main surface of a ceramic substrate, and firing the ceramic substrate. It is manufactured by singulating into pieces of a predetermined size.

Japanese Patent Application Laid-Open No. 2001-338806

However, in the electronic component manufacturing process described in Patent Document 1, when printing the electronic component on the ceramic substrate, when placing the ceramic substrate in a firing furnace, or when singulating the ceramic substrate, , various external forces act on the ceramic substrate. In this case, cracks are generated along the grain boundaries of the crystal grains forming the ceramic substrate, and damage such as cracks due to the cracks may occur in the ceramic substrate, making it difficult to obtain good electronic components. In recent years, with the demand for miniaturization of electronic components, ceramic substrates constituting electronic components also tend to be miniaturized and thinned. For this reason, the above-mentioned concern that the ceramic substrate may be damaged is becoming more serious.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a ceramic substrate that is difficult to break.

In order to achieve the above objects, the ceramic substrate of the present invention comprises a mounting area on which circuit elements constituting at least a part of a circuit are mounted, and a non-mounting area surrounding the mounting area and on which the circuit elements are not mounted. An average crystal grain size of crystal grains in the non-mounting region is larger than an average crystal grain size of crystal grains in the mounting region.

As described above, in the ceramic substrate of the present invention, the average crystal grain size of the crystal grains in the non-mounting region is larger than the average crystal grain size of the crystal grains in the mounting region. less. Since the number of crystal grain boundaries is reduced in this way, the number of fracture starting points in the non-mounting region is reduced, and the probability of fracture can be reduced. Therefore, even if an external force is applied to the non-mounting area, cracks generated in the non-mounting area can be reduced. Moreover, since cracks generated in the non-mounting region can be reduced in this way, cracks propagating from the non-mounting region to the mounting region can be reduced. Therefore, according to the ceramic substrate of the present invention, breakage such as cracking caused by such cracks can be suppressed.

It is preferable that the average crystal grain size of the crystal grains in the non-mounting region is 1.4 times or more the average crystal grain size of the crystal grains in the mounting region at least at the outer edge of the non-mounting region.

If the crystal grains in the non-mounting region have the above size, the grain boundaries of the crystal grains can be further reduced. Therefore, breakage of the ceramic substrate can be more effectively suppressed.

Further, an average crystal grain size of crystal grains in the non-mounting region may be 1.6 times or less as large as an average crystal grain size of crystal grains in the mounting region.

In this case, it is possible to effectively suppress the occurrence of grain boundaries in the mounting region.

Moreover, it is preferable that the non-mounting region has a bending strength that is 1.09 times or more the bending strength of the mounting region.

If the bending strength of the non-mounting region is such a magnitude, the occurrence of cracks in the non-mounting region can be effectively suppressed, and as a result, the occurrence of cracks in the mounting region can be more effectively suppressed. .

Also, the ceramic substrate may be made of aluminum oxide and magnesium oxide, and in this case, the aluminum oxide content is preferably 98% or more.

Moreover, the thickness of the ceramic substrate may be 0.1 mm or less.

Such ceramic substrates with a thickness of 0.1 mm or less are generally thinner than typical ceramic substrates used for chip resistors, for example. However, as described above, in the ceramic substrate of the present invention, the average crystal grain size in the non-mounting region is larger than the average crystal grain size in the mounting region. Therefore, even if the ceramic substrate is thin as described above, damage to the ceramic substrate can be suppressed.

As described above, according to the present invention, a ceramic substrate that is difficult to break is provided.

1 is a perspective view schematically showing a ceramic substrate of the present invention; FIG. FIG. 2 is a plan view of the ceramic substrate shown in FIG. 1; 3 is a graph showing the relationship between the position of the ceramic substrate in FIG. 2 and the average crystal grain size of the crystal grains at that position. FIG. 3 is a diagram showing how a ceramic green sheet for manufacturing the ceramic substrate in FIG. 2 is adjusted; It is a figure for demonstrating the small piece for a measurement. It is a graph which shows the bending strength of a ceramic substrate.

Hereinafter, embodiments for carrying out the ceramic substrate according to the present invention will be exemplified with accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention, and are not intended to limit and interpret the present invention. The present invention can be modified and improved from the following embodiments without departing from its gist. Note that in the drawings referred to below, the dimensions of each member may be changed to facilitate understanding.

FIG. 1 is a perspective view schematically showing a ceramic substrate 1 of the present invention, and FIG. 2 is a plan view of the ceramic substrate 1. As shown in FIG. As shown in FIGS. 1 and 2, the ceramic substrate 1 has a thin, substantially rectangular parallelepiped outer shape. For example, the length W in the longitudinal direction of the main surface of the ceramic substrate 1 may be 70 mm, the length L in the vertical direction perpendicular to the longitudinal direction of the main surface may be 60 mm, and the thickness H of the ceramic substrate 1 may be 0 mm. .1 mm or less.

This ceramic substrate 1 contains magnesium oxide and aluminum oxide as a main component. Note that aluminum nitride, mullite, or the like may be used as the main component. Also, the content of this main component can be changed as appropriate, but for example, it is preferably 90 wt % or more, more preferably 98 wt % or more, and even more preferably 99.9 wt % or more.

For example, when the main component of such a ceramic substrate 1 is aluminum oxide, a thin rectangular parallelepiped ceramic green sheet produced by, for example, a manufacturing method described later is fired at a temperature at which aluminum oxide can be sintered. It can be produced by The temperature is, for example, 1400° C. to 1800° C., more preferably 1500° C. to 1600° C. from the viewpoint of increasing the bending strength of the ceramic substrate 1, and a temperature of 1525° C. or 1550° C. further increases the bending strength. It is more preferable from the point of view. Note that the ceramic green sheet is a raw sheet that becomes a ceramic sintered body by firing.

A ceramic substrate 1 includes a mounting area 2 and a non-mounting area 3 .

The mounting area 2 is an area where electrodes, resistors, and the like as circuit elements forming at least a part of the circuit are mounted. The mounting area 2 is divided into a grid with boundaries 11 as boundaries. That is, one section of the divided mounting area 2 is defined as one board piece 10, and the electronic component is mounted on each main surface of each of these board pieces 10. As shown in FIG. The boundary 11 is virtually set to define the plurality of substrate pieces 10, and is indicated by broken lines in FIG. By singulating the mounting area 2 along this boundary 11 , a plurality of electronic components such as chip resistors can be obtained from one ceramic substrate 1 .

The singulation as described above may be performed, for example, by cutting using a laser or a dicing saw, or may be performed by forming dividing grooves in the boundary 11 to divide the mounting area 2 . The ceramic substrate 1 of the present embodiment has a thickness of 0.1 mm as described above, and is formed thinner than a general ceramic substrate for forming a chip resistor, for example. Therefore, it is preferable to separate the ceramic substrate 1 of the present embodiment into individual pieces by cutting using a laser.

The non-mounting area 3 is an area surrounding the mounting area 2, and is an area between the outer edge 3A of the ceramic substrate 1 and the outer edge 2A of the mounting area 2 positioned inward by the distance D from the outer edge 3A. Therefore, the outer edge 3A of the ceramic substrate 1 serves as the outer edge of the non-mounting area 3. As shown in FIG. The non-mounting region 3 is a region where electronic components are not mounted, and prevents external force from being applied directly to the mounting region 2 when electronic components are mounted on the mounting region 2 . The non-mounting area 3 is cut off from the mounting area 2 after the electronic component is mounted on the mounting area 2 . Although the distance D, which is the width of the non-mounting area 3, is not particularly limited, it is preferably set to a length sufficient to secure the range of the mounting area 2. FIG. For example, when the length W in the longitudinal direction of the ceramic substrate 1 is approximately 70 mm, the length L in the vertical direction is approximately 60 mm, and the thickness is approximately 0.1 mm, the distance D is preferably approximately 5 mm or less. If it is 4 mm or less, it is more preferable from the point that the range of the mounting area 2 can be sufficiently secured.

The ceramic substrate 1 of the present invention is configured such that the average crystal grain size of the crystal grains in the non-mounting region 3 is larger than the average crystal grain size of the crystal grains in the mounting region 2 .

FIG. 3 is a graph showing the relationship between the average crystal grain size of the crystal grains of the ceramic substrate 1 and the position of the ceramic substrate 1 in FIG. Points P1 to P4 in FIG. 3 correspond to points P1 to P4 in FIG. 2, respectively. Here, a point P1 in FIG. 2 is a region where a center line K extending in the longitudinal direction at the center of the ceramic substrate 1 in the vertical direction intersects with the outer edge 3A of the ceramic substrate 1, and is located in the non-mounting region 3. ing. Points P2 to P4 are areas on the center line K in the mounting area 2. Specifically, the point P2 is located inside the outer edge 3A by approximately ⅛ of the length W, and the point P3 is located inward from the outer edge 3A by approximately 1/4 of the length W, and the point P4 is located inward from the outer edge 3A by approximately 1/2 of the length W. Therefore, for example, when the length W is 70 mm, each of the points P2 to P4 is an area on the center line K at approximately 9 mm, 18 mm, and 35 mm inside the outer edge 3A.

The graph shown by the solid line in FIG. 3 shows a ceramic green sheet produced by, for example, a manufacturing method described later and fired at 1550° C., with a length W of approximately 70 mm, a length L of approximately 60 mm, and a thickness H of approximately 0.5 mm. It shows the average crystal grain size at points P1 to P4 of the ceramic substrate 1 having a dimension of 1 mm. In addition, the graph shown by the broken line in FIG. 3 is obtained by firing, for example, a ceramic green sheet produced by a manufacturing method described later at 1525 ° C., the length W is approximately 70 mm, the length L is approximately 60 mm, and the thickness H is approximately It shows the average crystal grain size at points P1 to P4 of the ceramic substrate 1 of 0.1 mm. As shown in FIG. 3, in the ceramic substrate 1, the average crystal grain size at the point P1 belonging to the non-mounting region 3 is larger than the average crystal grain size at the points P2 to P4 belonging to the mounting region 2. As shown in FIG. Specifically, in the ceramic substrate 1 of the present embodiment, the average grain size of the point P1 belonging to the non-mounting region 3 is about 1.4 times or more the average grain size of the points P2 to P4 belonging to the mounting region 2. 1.6 times or less.

Such an average crystal grain size can be measured, for example, as follows. First, each of the points P1 to P4 is observed with a field emission scanning electron microscope to obtain an observed image. After that, lines are drawn along the grain boundaries of the crystal grains shown in the observed image, and the observed image is binarized using image processing software “Image-J”. Based on the binarized image, the grain size of each crystal grain is calculated as the Feret diameter, and the average value of the calculated Feret diameters is obtained. In this manner, the average crystal grain size of the crystal grains at each of the points P1 to P4 can be obtained.

Further, the ceramic substrate 1 having a configuration in which the average crystal grain size of the crystal grains in the non-mounting region 3 is larger than the average crystal grain size of the crystal grains in the mounting region 2 is a ceramic green sheet prepared as follows, for example. can be made by firing

First, as shown in FIG. 4, a mold 90 is prepared. The mold 90 has a substantially rectangular shape when viewed from above, and includes an inner wall 91 and an outer wall 92 . The area surrounded by the inner wall 91 is the first space 93 , and the space between the inner wall 91 and the outer wall 92 is the second space 94 . Next, an aluminum oxide powder, a magnesium oxide powder, a sintering aid, an organic binder, a solvent, a plasticizer, etc. are appropriately mixed to prepare a slurry S1, and the first space 93 of the mold 90 is filled with the slurry S1. . Next, an aluminum oxide powder having a larger crystal grain than the aluminum oxide powder in the slurry S1, a magnesium oxide powder similar to the slurry S1, a sintering aid, an organic binder, a solvent, a plasticizer, etc. are appropriately mixed to form a slurry S2. is adjusted, and the second space 94 of the mold 90 is filled with this slurry S2. After that, the mold 90 is removed, and the slurries S1 and S2 are heated and pressurized. For example, in this way, a ceramic green sheet from which the ceramic substrate 1 can be manufactured can be prepared.

As described above, the ceramic substrate 1 of the present embodiment includes a mounting area 2 in which circuit elements constituting at least a part of a circuit are mounted, a non-mounting area 3 surrounding the mounting area 2 and in which no circuit elements are mounted, and the average crystal grain size of the crystal grains in the non-mounting region 3 is larger than the average crystal grain size of the crystal grains in the mounting region 2 .

With such a configuration, the number of crystal grain boundaries in the non-mounting region 3 is smaller than that in the mounting region 2 in the ceramic substrate 1 of the present embodiment. Since the crystal grain boundaries are reduced in this way, the number of fracture starting points in the non-mounting region 3 is reduced, and the probability of fracture is reduced. . For example, as will be described later, in the ceramic substrate 1 obtained by firing the ceramic green sheet at 1525° C., the bending strength of the non-mounting region 3 is approximately 1.09 times or more greater than the bending strength of the mounting region 2. In the ceramic substrate 1 obtained by firing the ceramic green sheet at 1550° C., the bending strength of the non-mounting region 3 can be approximately 1.11 times or more greater than the bending strength of the mounting region 2 . Therefore, even if an external force is applied to the non-mounting area 3, cracks occurring in the non-mounting area 3 can be reduced. In addition, since cracks generated in the non-mounting region 3 can be reduced in this way, cracks propagating from the non-mounting region 3 to the mounting region 2 can be reduced. Therefore, according to the ceramic substrate 1 of the present invention, breakage such as cracks caused by such cracks can be suppressed.

Further, according to the ceramic substrate 1 of the present embodiment, as described above, at least at the outer edge of the non-mounting region 3, the average crystal grain size of the crystal grains in the non-mounting region 3 is equal to the average crystal grain size of the crystal grains in the mounting region 2. It should be 1.4 times or more the particle size. If the crystal grains in the non-mounting region 3 have such a size, the number of crystal grain boundaries is reduced. Therefore, breakage of the ceramic substrate can be suppressed more effectively.

Further, in the ceramic substrate 1 of the present embodiment, as described above, the average crystal grain size of the crystal grains in the non-mounting region 3 is 1.6 times or less the average crystal grain size of the crystal grains in the mounting region 2. .

As shown in FIG. 3, the average crystal grain size of the crystal grains of the ceramic substrate 1 gradually decreases in the area from the outer edge 3A of the ceramic substrate 1 to the vicinity of the boundary between the mounting area 2 and the non-mounting area 3. , the mounting region 2 where the average crystal grain size is the smallest, for example, the region from the point P2 to the central point P4, tends to be approximately the same. Therefore, if the average crystal grain size of the crystal grains in the non-mounting region 3 is too large compared to the average crystal grain size of the crystal grains in the mounting region 2, the average crystal grain size will change in the region where the average crystal grain size gradually decreases. can be steep. For example, the slope of change in average grain size from point P1 to point P2 in FIG. 3 can be steep. In this case, for example, the average crystal grain size of the region located on the non-mounting region 3 side of the point P2 in the mounting region 2 and the average crystal grain size of the regions inside the point P2, such as the points P3 and P4. Differences can occur between As described above, if the average crystal grain size differs in the mounting region 2 , the number of crystal grain boundaries may vary in the mounting region 2 .

On the other hand, by setting the upper limit of the average crystal grain size of the crystal grains in the non-mounting region 3 to 1.6 times the average crystal grain size of the crystal grains in the mounting region 2, in the region where the average crystal grain size gradually decreases The slope of the change in the average crystal grain size is suppressed from becoming steep, and the occurrence of large or small crystal grain boundaries in the mounting region 2 can be effectively suppressed. Therefore, for example, when the mounting region 2 is singulated, it is possible to more effectively suppress variations in the quality of the individual board pieces 10 to be singulated.

In addition, the ceramic substrate 1 of the present embodiment has a thickness of 0.1 mm or less, as described above, and is generally thinner than, for example, general ceramic substrates used for chip resistors. However, as described above, in the ceramic substrate 1 of the present invention, the average crystal grain size of the non-mounting region 3 is larger than the average crystal grain size of the mounting region 2. Damage to the ceramic substrate due to cracks or the like can be suppressed.

As described above, the ceramic substrate 1 according to the present invention has been described as an example of the above embodiment, but the present invention is not limited to this.

For example, in the above embodiment, the average crystal grain size of the crystal grains in the outer edge of the non-mounting region 3 is 1.4 times or more the average crystal grain size of the crystal grains in the mounting region 2 . However, the average crystal grain size of the crystal grains in the outer edge of the non-mounting region 3 may be larger than 1 time and smaller than 1.4 times the average crystal grain size of the crystal grains in the mounting region 2 . Even in this case, if the average crystal grain size of the crystal grains in the non-mounting region 3 is larger than the average crystal grain size of the crystal grains in the mounting region 2, breakage of the ceramic substrate due to the cracks can be suppressed. .

Further, in the above embodiment, an example has been described in which the average crystal grain size of the crystal grains in the non-mounting region 3 is 1.6 times or less the average crystal grain size of the crystal grains in the mounting region 2 . However, if the average crystal grain size of the crystal grains in the non-mounting region 3 is larger than the average crystal grain size of the crystal grains in the mounting region 2, the average crystal grain size of the crystal grains in the non-mounting region 3 The upper limit need not be 1.6 times the average crystal grain size of the crystal grains in the mounting region 2, and may be 1.6 times or more. Even in this case, the bending strength in the non-mounting region 3 can be made larger than the bending strength in the mounting region 2, and cracks transmitted from the non-mounting region 3 to the mounting region 2 can be reduced.

Also, in the above embodiment, an example in which the thickness of the ceramic substrate is 0.1 mm or less has been described, but the thickness of the ceramic substrate may be greater than 0.1 mm. Even in this case, if the average crystal grain size of the crystal grains in the non-mounting region 3 is larger than the average crystal grain size of the crystal grains in the mounting region 2, breakage of the ceramic substrate due to the cracks can be suppressed. .

EXAMPLES The present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

(Example 1)
The inventors conducted the following experiments in order to verify the effects of the ceramic substrate 1 of the present invention.

First, the inventors prepared four ceramic substrates 1 fired at 1550° C. having a configuration in which the average crystal grain size of the crystal grains in the non-mounting region 3 was larger than the average crystal grain size of the crystal grains in the mounting region 2. prepared a piece. The average crystal grain size of these ceramic substrates 1 was calculated by the method described above. That is, an observed image obtained by observing each of the points P1 to P4 of each ceramic substrate 1 with a field emission scanning electron microscope is binarized with image processing software "Image-J", and each calculated value is It was obtained as an average value of Feret diameters of crystal grains. This ceramic substrate 1 was manufactured to have a length W of 70 mm, a length L of 60 mm, and a thickness H of 0.1 mm. In this example, the points P2 to P4 observed with the field emission scanning electron microscope are regions 9 mm inside, 18 mm inside, and 35 mm inside from the outer edge 3A of the ceramic substrate 1 shown in FIG.

Next, 20 sheets each of four types of measuring pieces Fr1, Fr2, Fr3, and Fr4 for measuring bending strength were prepared by the following method.

First, as shown in FIG. 5, one of the four ceramic substrates 1 is picked up, and a portion 5 mm inward in the vertical direction from one outer edge 3Ab1 of the ceramic substrate 1 in the vertical direction is cut in the longitudinal direction. cut along. Similarly, a portion 5 mm inside from the other outer edge 3Ab2 in the vertical direction was cut along the longitudinal direction. These two severed cuts UN are indicated by hatching.

Next, a strip St1 was produced by cutting a portion 2.4 mm inside from the outer edge 3Aa in the longitudinal direction of the ceramic substrate 1A along the vertical direction. That is, the strip St1 is a strip including the outer edge 3Aa of the ceramic substrate 1 and includes the point P1. Next, the strip St1 was cut into 5 equal parts to produce 5 measurement pieces Fr1. That is, each measuring piece Fr1 has a thickness of 0.1 mm and a main surface measuring 2.4 mm×10 mm.

Next, a strip St2 was produced by vertically cutting a portion 7.8 mm inward from the outer edge 3Aa and a portion 10.2 mm inward from the outer edge 3Aa. That is, the strip St2 includes a portion 9 mm inward from the outer edge 3Aa of the ceramic substrate 1 in the longitudinal direction, and includes the point P2. Next, the strip St2 was cut into 5 equal pieces to produce 5 small measurement pieces Fr2. Each measuring strip Fr2 thus has a thickness of 0.1 mm and a main surface measuring 2.4 mm×10 mm.

Similarly, strips St3 and St4 were produced. The strip St3 includes a portion 18 mm inside the outer edge 3Aa of the ceramic substrate 1 in the longitudinal direction, and includes the point P3. Moreover, the strip St4 includes a portion 35 mm inward from the outer edge 3Aa of the ceramic substrate 1 in the longitudinal direction, and includes the point P4. After that, each of the strips St3 and St4 was divided into 5 equal pieces to prepare measurement pieces Fr3 and Fr4. Each of the strips St3 and St4 has a thickness of 0.1 mm and a main surface measuring 2.4 mm×10 mm.

The remaining three ceramic substrates 1 were subjected to the same process as described above, and from each of the three ceramic substrates 1, five measuring pieces Fr1 to Fr4 were produced. In this way, 20 measuring pieces Fr1 to Fr4 were produced.

Next, the bending strength of each of the 20 measurement pieces Fr1 to Fr4 was measured. In this example, a Tensilon universal material testing machine RTG-1225 (manufactured by A&D Co., Ltd.) was used to measure the bending strength of the measuring pieces Fr1 to Fr4. Specifically, each measurement piece Fr1 to Fr4 is put in the tester, and the bending strength (MPa ) was measured. Then, after deleting the data showing abnormal values among the measured data, the bending strength data is plotted on a Weibull graph for each of the measurement pieces Fr1 to Fr4, and the Weibull of each of the measurement pieces Fr1 to Fr4 is plotted. Scale parameters (MPa) of the distribution were obtained, and these scale parameters were used as the bending strengths of the measuring pieces Fr1 to Fr4. This result is indicated by a solid line in FIG.

As described above, since the measuring piece Fr1 includes the outer edge 3Aa of the ceramic substrate 1, the bending strength of the measuring piece Fr1 can be considered as the bending strength at the point P1. The measurement pieces Fr2 to Fr4 are measurement pieces including portions positioned 9 mm, 18 mm, and 35 mm inward from the outer edge 3A of the ceramic substrate 1A. Therefore, the bending strength of the measuring piece Fr2 is the bending strength at the point P2, the bending strength of the measuring piece Fr3 is the bending strength at the point P3, and the bending strength of the measuring piece Fr4 is the bending strength at the point P3. can be considered as the bending strength at P4.

As shown by the solid line in FIG. 6, in this example in which the ceramic green sheet was fired at 1550° C., the bending strength at point P1 of the ceramic substrate 1 is greater than the bending strength at points P2 to P4. . Specifically, the bending strength at point P1 was 455.0 MPa, and the bending strength at point P4, which shows the maximum bending strength among points P2 to P4, was 417.3 MPa. That is, when the ceramic green sheet described above is fired at 1550° C., the bending strength in the outer edge region from the outer edge 3A of the ceramic substrate 1 to the portion 2.4 mm inside is lower than that of the inner region located inside the outer edge region. It was found to be 1.09 times or more greater than the bending strength.

(Example 2)
The inventors also measured the bending strength of the ceramic substrate 1 by the same method except that the firing temperature of the ceramic substrate 1 was set to 1525°C. The result is shown by a dashed line in FIG.

As shown in FIG. 6, in the ceramic substrate 1 fired at 1525° C. as well as the ceramic substrate 1 in Example 1 fired at 1550° C., the bending strength at the point P1 of the ceramic substrate 1 is reduced to the point P2. It can be seen that the bending strength is greater than that at P4. Specifically, the bending strength at the point P1 was 477.1 MPa, and the bending strength at the point P3 showing the maximum bending strength among the points P2 to P4 was 428.9 MPa. That is, in the ceramic substrate 1 fired at 1525° C., the flexural strength in the outer edge region from the outer edge 3A of the ceramic substrate 1 to the portion 2.4 mm inward is the flexural strength of the inner region located inside the outer edge region. It was found to be 1.11 times greater than the strength.

As described above, in the ceramic substrate 1 of the present invention, the bending strength of the outer edge region of the ceramic substrate 1 was found to be greater than the bending strength of the inner region.

Therefore, according to the ceramic substrate of the present invention, the area 2.4 mm inside from the outer edge of the ceramic substrate 1 is defined as the non-mounting area 3, and the area inside the non-mounting area 3 is defined as the mounting area 2. The bending strength of the mounting area 3 can be made 1.09 times or more greater than the bending strength of the mounting area 2 . Therefore, even if an external force is applied to the non-mounting region, cracks generated in the non-mounting region can be reduced, and cracks transmitted from the non-mounting region to the mounting region can be reduced. It is possible to suppress damage such as

INDUSTRIAL APPLICABILITY According to the present invention, a ceramic substrate that is difficult to break is provided, and can be used in the field of electronic components such as chip resistors.

Reference Signs List 1... Ceramic substrate 2... Mounting area 3... Non-mounting area 3A... Outer edge

Claims (7)

a mounting area in which circuit elements constituting at least part of a circuit are mounted;
a non-mounting region that surrounds the mounting region and in which the circuit element is not mounted;
with
A ceramic substrate, wherein an average crystal grain size of crystal grains in the non-mounting region is larger than an average crystal grain size of crystal grains in the mounting region. 4. An average crystal grain size of crystal grains in the non-mounting region is 1.4 times or more as large as an average crystal grain size of the crystal grains in the mounting region, at least at an outer edge of the non-mounting region. 2. The ceramic substrate according to 1. 3. The ceramic substrate according to claim 1, wherein an average crystal grain size of crystal grains in said non-mounting region is 1.6 times or less as large as an average crystal grain size of crystal grains in said mounting region. 4. The ceramic substrate according to claim 1, wherein the bending strength of the non-mounting area is 1.09 times or more the bending strength of the mounting area. 5. The ceramic substrate according to claim 1, wherein the ceramic substrate is made of aluminum oxide and magnesium oxide. 6. The ceramic substrate according to claim 5, wherein the aluminum oxide content is 98% or more. 7. The ceramic substrate according to any one of claims 1 to 6, having a thickness of 0.1 mm or less.

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