Ceramic component

Abstract

The present disclosure addresses the problem of providing a ceramic component that makes it possible to reduce the occurrence of solder cracks. A ceramic component 1 includes: a rectangular-parallelepiped ceramic element body 10 for which a first direction is aligned with long edges thereof; a first external electrode 21 which wraps around a first ridge line part R1 between a first end surface S11, and a first principal surface S31 or a second principal surface S32; a second external electrode 22 which wraps around a second ridge line part R2 between a second end surface S12, and the first principal surface S31 or the second principal surface S32; and a third external electrode 23 which wraps around a third ridge line part R3 between a first side surface S21, and the first principal surface S31 or the second principal surface S32. A first curvature radius of the first external electrode 21 at the first ridge line part R1 and a second curvature radius of the second external electrode 22 at the second ridge line part R2 are larger than a third curvature radius of the third external electrode 23 at the third ridge line part R3.

Description

Ceramic parts

[0001] The present disclosure relates to ceramic components, and more particularly to ceramic components having external electrodes.

[0002] Various ceramic components such as varistors are used in various electronic devices, electronic equipment, etc. Varistors are used to protect various electronic devices, electronic equipment, etc. from abnormal voltages caused by lightning surges, static electricity, etc., and to prevent malfunctions of electronic devices, electronic equipment, etc. caused by noise generated in circuits.

[0003] In recent years, electronic devices such as smartphones and tablet terminals have become smaller, thinner, and lighter, which has led to a demand for higher density in component mounting technology.

[0004] Patent Document 1 discloses a chip capacitive varistor. This chip capacitive varistor is characterized by comprising a sheet-like substrate having voltage nonlinear resistance ceramic, and a plurality of pairs of internal electrodes sandwiching the substrate, at least one of which is electrically non-contact with the other. This chip capacitive varistor is said to be able to improve packaging density.

[0005] However, when conventional ceramic components such as the chip capacitive varistor described in Patent Document 1 are mounted on a printed circuit board or the like by soldering and subjected to temperature fluctuations, the difference in thermal expansion coefficients between the ceramic component and the printed circuit board or the like can cause solder distortion at the solder joint connecting the ceramic component to the printed circuit board or the like, which can result in solder cracks, which can cause the component to fall off or lead to poor connections.

[0006] Japanese Patent Application Publication No. 07-235406

[0007] An object of the present disclosure is to provide a ceramic component that can reduce the occurrence of solder cracks.

[0008] A ceramic component according to one aspect of the present disclosure includes a rectangular parallelepiped ceramic body having first end faces and second end faces opposing each other in a first direction, first side faces and second side faces opposing each other in a second direction, and first main faces and second main faces opposing each other in a third direction, the ceramic body having a longer side in the first direction; a first external electrode provided on the first end face, wrapping around a first ridge portion between the first end face and the first main face or the second main face, and covering a portion of the first main face and a portion of the second main face; a second external electrode provided on the second end face, wrapping around a second ridge portion between the second end face and the first main face or the second main face, and covering a portion of the first main face and a portion of the second main face; and a third external electrode provided on the first side face, wrapping around a third ridge portion between the first side face and the first main face or the second main face, and covering a portion of the first main face and a portion of the second main face. A first radius of curvature of the first external electrode at the first ridge portion and a second radius of curvature of the second external electrode at the second ridge portion are larger than a third radius of curvature of the third external electrode at the third ridge portion.

[0009] FIG. 1 is a schematic perspective view showing an example of the ceramic part according to the present embodiment.

[0010] 1. Overview Hereinafter, an overview of the ceramic component 1 will be described with reference to the drawings. Note that the drawings are schematic diagrams, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

[0011] In the following description, the X-axis direction parallel to the long side direction of the ceramic body 10 is defined as a first direction, the Y-axis direction as a second direction, and the Z-axis direction as a third direction, as shown in Fig. 1. However, these directions are merely examples and are not intended to limit the directions in which the ceramic component 1 may be used.

[0012] The inventors, through intensive research aimed at solving the above-mentioned problems, discovered that there is a relationship between the partial shapes of each component of a ceramic component and the occurrence of solder cracks, and thus completed the present disclosure.

[0013] As shown in FIG. 1, the ceramic component 1 of this embodiment includes a ceramic body 10 and external electrodes, that is, a first external electrode 21, a second external electrode 22, and a third external electrode 23.

[0014] The ceramic body 10 is rectangular with its long sides in the first direction (X-axis direction), and has a first end face S11 and a second end face S12 that face each other in the first direction (X-axis direction), a first side face S21 and a second side face S22 that face each other in the second direction (Y-axis direction), and a first main face S31 and a second main face S32 that face each other in the third direction (Z-axis direction).

[0015] The first external electrode 21 is provided on the first end face S11, wraps around a first ridge R1 between the first end face S11 and the first main face S31 or the second main face S32, and covers a part of the first main face S31 and a part of the second main face S32. The second external electrode 22 is provided on the second end face S12, wraps around a second ridge R2 between the second end face S12 and the first main face S31 or the second main face S32, and covers a part of the first main face S31 and a part of the second main face S32. The third external electrode 23 is provided on the first side face S21, wraps around a third ridge R3 between the first side face S21 and the first main face S31 or the second main face S32, and covers a part of the first main face S31 and a part of the second main face S32.

[0016] In the ceramic component 1 of this embodiment, the first radius of curvature (hereinafter also referred to as radius of curvature (I-1)) of the first external electrode 21 at the first ridge portion R1 and the second radius of curvature (hereinafter also referred to as radius of curvature (I-2)), and the radii of curvature (I-1) and the radii of curvature (I-2) are collectively referred to as radius of curvature (I)) of the second external electrode 22 at the second ridge portion R2 are larger than the third radius of curvature (hereinafter also referred to as radius of curvature (II)) of the third external electrode 23 at the third ridge portion R3.

[0017] The ceramic component 1 of this embodiment can reduce the occurrence of solder cracks. The reason why the ceramic component 1 of this embodiment has the above-described configuration and exhibits the above-described effect is thought to be related to, for example, differences in shape and in contact area with the solder between the first external electrode 21 and the second external electrode 22, which are end electrodes, and the third external electrode 23, which is a side electrode, of the ceramic component 1. Another reason is thought to be the difference between the end electrodes 21 and 22, which wrap around four faces (S21, S22, S31, S32), and the side electrodes 23 and 24, which wrap around two faces (S31, S32). Another reason is thought to be the fact that the shape of the ceramic body 10 is a rectangular parallelepiped with its long sides in the first direction.

[0018] As described above, according to the present disclosure, it is possible to provide a ceramic component that can reduce the occurrence of solder cracks.

[0019] 2. Details <Ceramic Component> The ceramic component 1 of this embodiment includes a ceramic body 10 and external electrodes, which are a first external electrode 21, a second external electrode 22, and a third external electrode 23. As shown in FIG. 1 , the ceramic component 1 typically includes a fourth external electrode 24 that is provided on the second side surface S22, wraps around a fourth ridge R4 between the second side surface S22 and the first main surface S31 or the second main surface S32, and covers a portion of the first main surface S31 and a portion of the second main surface S32. The ceramic component 1 may also include plated electrodes that are provided so as to cover at least a portion of the surface of each of the external electrodes 21, 22, 23, and 24. The ceramic component 1 typically includes a plurality of internal electrodes within the ceramic body 10.

[0020] As described above, the ceramic component 1 in FIG. 1 is a four-terminal type, and is typically used by connecting the first external electrode 21 and the second external electrode 22, which are end surface electrodes, to two electronic devices or the like, respectively, and connecting the third external electrode 23 and the fourth external electrode 24, which are side surface electrodes, to ground (GND).

[0021] In the ceramic component 1, the term "ridgeline portion" refers to a curved region of the external electrode or ceramic body in cross section near an edge where two surfaces, a surface including the end surface S11 or S12 or the side surface S21 or S22 of the ceramic body 10, intersect with a surface including the main surface S31 or S32. The "radius of curvature" of the ridgeline portion refers to the radius of an arc in the shape of the outermost edge of the curved region of the external electrode or ceramic body in cross section. The radius of curvature can be calculated, for example, using a known mathematical method from three points on a curve included in the outermost edge of the curved region in cross section: the start point, the end point, and a point located midway between the start point and the end point. The radius of curvature is, for example, the value of the radius of curvature measured at the center point of the ridgeline portion. Furthermore, "radius of curvature (a) is larger than radius of curvature (b)" means that radius of curvature (a) is 1.05 times or more larger than radius of curvature (b).

[0022] The ceramic component 1 has, as the first ridgeline R1, a ridgeline R1A between the first end face S11 and the first main surface S31 and a ridgeline R1B between the first end face S11 and the second main surface S32. The ceramic component 1 has, as the second ridgeline R2, a ridgeline R2A between the second end face S12 and the first main surface S31 and a ridgeline R2B between the second end face S12 and the second main surface S32. The ceramic component 1 has, as the third ridgeline R3, a ridgeline R3A between the first side face S21 and the first main surface S31 and a ridgeline R3B between the first side face S21 and the second main surface S32. The ceramic component 1 has, as the fourth ridgeline R4, a ridgeline R4A between the second side face S22 and the first main surface S31 and a ridgeline R4B between the second side face S22 and the second main surface S32.

[0023] Examples of the ceramic component 1 of this embodiment include a varistor, a thermistor, a ceramic capacitor, etc. Hereinafter, an example in which the ceramic component 1 of this embodiment is a varistor 1 will be described.

[0024] [Ceramic Element Body] The shape of the ceramic element body 10 in the varistor 1 of this embodiment is a rectangular parallelepiped with the longer sides in the first direction (X-axis direction). The dimensions of the ceramic element body 10 are, for example, a length in the first direction (X-axis direction) of 0.6 to 1.6 mm, a length (width) in the second direction (Y-axis direction) of 0.3 to 0.8 mm, and a length (height) in the third direction (Z-axis direction) of 0.3 to 0.8 mm. The corners of the ceramic element body 10 are chamfered or the like to form rounded ridges.

[0025] In the varistor 1, the ceramic body 10 is made of, for example, a semiconductor ceramic component having non-linear resistance characteristics. The ceramic body 10 usually contains ZnO as a main component and Bi as a secondary component. ２ O ３ , Co ２ O ３ , MnO ２ , Sb ２ O ３ , Pr ６ O １１ , CaCO ３ , Cr ２ O ３ The ceramic body 10 is formed by the semiconductor ceramic components, in which the main component such as ZnO is solid-solution sintered with some of the secondary components, and the remaining secondary components are precipitated at the grain boundaries.

[0026] A plurality of internal electrodes are arranged inside the ceramic body 10. The number of internal electrodes in the varistor 1 is, for example, three, and the three internal electrodes are electrically connected to a first external electrode 21, a second external electrode 22, a third external electrode 23, and a fourth external electrode 24, respectively.

[0027] The internal electrodes contain a metal such as Ag, Pd, PdAg, PtAg, etc. The ceramic body 10 having the internal electrodes 12 therein can be produced by applying an internal electrode paste containing the metal to ceramic sheets prepared using a slurry containing, for example, ZnO, stacking, pressing, and cutting the obtained ceramic sheets, removing the binder at a temperature of, for example, 300°C or higher and 500°C or lower, and then firing at a temperature of, for example, 600°C or higher and 1100°C or lower.

[0028] In the ceramic body 10, the radius of curvature at the first ridgeline R1 (hereinafter also referred to as the radius of curvature (A-1)) and the radius of curvature at the second ridgeline R2 (hereinafter also referred to as the radius of curvature (A-2), and the radii of curvature (A-1) and the radii of curvature (A-2) are collectively referred to as the radius of curvature (A)) are typically smaller than the radius of curvature at the third ridgeline R3 (hereinafter also referred to as the radius of curvature (B)). In other words, the radius of curvature (A-1) of the ceramic body 10 at the first ridgeline R1 and the radius of curvature (A-2) of the ceramic body 10 at the second ridgeline R2 are typically smaller than the radius of curvature (B) of the ceramic body 10 at the third ridgeline R3.

[0029] Due to the manufacturing method, the ceramic element 10 manufactured by the above-described method typically has a smaller radius of curvature (A) than radius of curvature (B). Even if the ceramic element 10 used for manufacturing has such a shape, the ceramic component 1 of this embodiment can reduce the occurrence of solder cracks by making the radius of curvature (I) of the external electrodes larger than the radius of curvature (II).

[0030] [External Electrodes] As shown in FIG. 1, the varistor 1 is provided with a first external electrode 21, a second external electrode 22, a third external electrode 23, and a fourth external electrode 24 as external electrodes.

[0031] In the varistor 1, the first and second radii of curvature are larger than the third radius of curvature. That is, the radius of curvature (I) is larger than the radius of curvature (II). In this way, the varistor 1 can reduce the occurrence of solder cracks.

[0032] The ratio of the first and second curvature radii to the third curvature radius is preferably 1.1 or greater. In other words, the ratio of the curvature radius (I) to the curvature radius (II) (curvature radius (I) / curvature radius (II)) is preferably 1.1 or greater. In this case, the varistor 1 can further reduce the occurrence of solder cracks.

[0033] The ratio of radius of curvature (I) / radius of curvature (II) is preferably 1.15 or more, more preferably 1.2 or more, even more preferably 1.3 or more, and particularly preferably 1.35 or more. The upper limit of the ratio is, for example, 8 or less, preferably 5.0 or less, more preferably 3.0 or less, even more preferably 2.0 or less, and particularly preferably 1.5 or less. In these cases, the varistor 1 can further reduce the occurrence of solder cracks.

[0034] The radius of curvature (I) is, for example, 0.055 mm or more, preferably 0.060 mm or more, and more preferably 0.070 mm or more. The radius of curvature (II) is, for example, 0.045 mm or more, more preferably 0.050 mm or more, and even more preferably 0.055 mm or more. The upper limits of the radius of curvature (I) and the radius of curvature (II) are, for example, 0.2 mm or less, and preferably 0.1 mm or less.

[0035] The external electrodes 21, 22, 23, 24 are formed on the side surfaces S11, S12, S21, S22, etc. of the ceramic body 10 by using a metal component such as Ag, AgPd, AgPt, etc. and Bi. ２ O ３ , SiO ２ , B ２ O ３ The external electrodes 21, 22, 23, 24 are formed by applying an external electrode paste containing glass components such as tantalum and tantalum oxide by dipping, printing, or the like, and then baking the paste at a temperature of, for example, 700° C. to 800° C. In other words, the external electrodes 21, 22, 23, 24 are usually sintered metal bodies. When the external electrodes are sintered metal bodies, solder distortion and solder cracks are likely to occur, particularly at the soldered connections, and therefore, there are great benefits to adopting the present disclosure.

[0036] The values ​​of the radius of curvature (I) and the radius of curvature (II) can be changed, for example, by adjusting the thickness of each of the external electrodes 21, 22, 23, and 24 to be formed, adjusting the viscosity of each of the external electrode pastes that form the external electrodes, adjusting the method of applying the external electrode paste to each of the external electrodes, adjusting the radius of curvature (A) and the radius of curvature (B) in the ceramic body 10, etc.

[0037] [Plating Electrodes] The plating electrodes are provided so as to cover at least a portion of each of the external electrodes 21, 22, 23, and 24. The plating electrodes include, for example, Ni electrodes provided so as to cover at least a portion of each of the external electrodes 21, 22, 23, and 24, and Sn electrodes provided so as to cover at least a portion of each of the Ni electrodes.

[0038] It is believed that the ceramic component 1 of this embodiment, such as a thermistor or ceramic capacitor other than the varistor 1, can also reduce the occurrence of solder cracks.

[0039] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0040] <Manufacturing of Ceramic Parts> Ceramic parts were manufactured by applying an external electrode paste to the surface of a ceramic body containing ZnO as the main component and then baking the paste. By varying the thickness of the formed external electrodes, ceramic parts of Comparative Example 1, Example 1, and Example 2 were obtained.

[0041] <Evaluation> [Radius of curvature] For each of the manufactured ceramic components, the radius of curvature (I) of the first and second external electrodes, which are end electrodes, and the radius of curvature (II) of the third external electrode, which is a side electrode, were measured. [Solder crack length] Each of the manufactured ceramic components was solder-mounted on a printed circuit board, and the ceramic components solder-mounted on the printed circuit board were subjected to a thermal shock test in which the temperature was fluctuated 2,000 times between 125°C and -40°C for an exposure time of 3 minutes, and the length (mm) of a solder crack originating from the solder connection between the element body and the solder was measured. The solder crack length (%) was defined as the length of the uncracked portion, where the shortest distance from the end of the crack to the end of the solder fillet is the length of the uncracked portion, and is calculated as follows: solder crack length × 100 / (solder crack length + uncracked portion length) (%).

[0042] Table 1 below shows the values ​​(mm) of the radius of curvature (I) and the radius of curvature (II), the ratio of the radius of curvature (I) / the radius of curvature (II), and the measured values ​​(%) of the solder crack length for the ceramic parts of Comparative Example 1, Example 1, and Example 2.

[0043]

[0044] As is clear from the results in Table 1, the ceramic parts of Examples 1 and 2 have a larger radius of curvature (I) at the end electrode than the radius of curvature (II) at the side electrode, and are able to reduce the occurrence of solder cracks compared to the ceramic part of Comparative Example 1.

[0045] (Summary) As is clear from the above embodiment, the present disclosure includes the following aspects. In the following, reference numerals are given in parentheses only to clarify the correspondence with the embodiment.

[0046] The ceramic part (1) of the first aspect has a first end face (S11) and a second end face (S12) that face each other in a first direction, a first side face (S21) and a second side face (S22) that face each other in a second direction, and a first main face (S31) and a second main face (S32) that face each other in a third direction, and includes a rectangular parallelepiped ceramic body (10) with its long sides in the first direction, and a first ridge portion (R1) that is provided on the first end face (S11) and wraps around a first ridge portion (R1) between the first end face (S11) and the first main face (S31) or the second main face (S32), and extends to a part of the first main face (S31) and the second main face (S32). The semiconductor device is provided with a first external electrode (21) covering a portion of the main surface (S32), a second external electrode (22) provided on the second end surface (S12) and wrapping around a second ridge portion (R2) between the second end surface (S12) and the first main surface (S31) or the second main surface (S32), covering a portion of the first main surface (S31) and a portion of the second main surface (S32), and a third external electrode (23) provided on the first side surface (S21) and wrapping around a third ridge portion (R3) between the first side surface (S21) and the first main surface (S31) or the second main surface (S32), covering a portion of the first main surface (S31) and a portion of the second main surface (S32). The first radius of curvature of the first external electrode (21) at the first ridge portion (R1) and the second radius of curvature of the second external electrode (22) at the second ridge portion (R2) are larger than the third radius of curvature of the third external electrode (23) at the third ridge portion (R3).

[0047] According to the first aspect, the ceramic component (1) can reduce the occurrence of solder cracks.

[0048] In the ceramic part (1) of the second aspect, in the first aspect, the ratio of the first radius of curvature and the second radius of curvature to the third radius of curvature is 1.1 or more.

[0049] According to the second aspect, the ceramic part (1) can further reduce the occurrence of solder cracks.

[0050] In the ceramic part (1) of the third aspect, in the ceramic body (10) of the first or second aspect, the radius of curvature of the first ridgeline portion (R1) and the radius of curvature of the second ridgeline portion (R2) are smaller than the radius of curvature of the third ridgeline portion (R3).

[0051] According to the third aspect, even if the ceramic body (10) has the above-described shape, by adjusting the radii of curvature of the ridge portions (R1, R2, R3) of the external electrodes (21, 22, 23), the ceramic component (1) can reduce the occurrence of solder cracks.

[0052] In the ceramic part (1) of the fourth aspect, in any one of the first to third aspects, the first external electrode (21), the second external electrode (22), and the third external electrode (23) are made of a metal sintered body.

[0053] According to the fourth aspect, when the external electrodes (21, 22, 23) are sintered metal bodies, the benefits of employing the present disclosure are particularly great.

[0054] A ceramic component (1) of a fifth aspect is any one of the first to fourth aspects, further comprising a fourth external electrode (24) provided on the second side surface (S22), wrapping around a fourth ridge portion (R4) between the second side surface (S22) and the first main surface (S31) or the second main surface (S32), and covering a part of the first main surface (S31) and a part of the second main surface (S32). The first radius of curvature and the second radius of curvature are larger than the fourth radius of curvature of the fourth external electrode (24) at the fourth ridge portion (R4).

[0055] According to the fifth aspect, even when the ceramic component (1) has a fourth external electrode (24) that is provided on the second side surface (S22) and wraps around the fourth ridge portion (R4), the occurrence of solder cracks can be reduced.

[0056] REFERENCE SIGNS LIST 1 Ceramic component (varistor) 10 Ceramic body 21 First external electrode 22 Second external electrode 23 Third external electrode 24 Fourth external electrode S11 First end face S12 Second end face S21 First side face S22 Second side face S31 First main face S32 Second main face R1 First ridge R2 Second ridge R3 Third ridge R4 Fourth ridge

Claims

1. A rectangular parallelepiped ceramic element body having first end faces and second end faces opposing each other in a first direction, first side faces and second side faces opposing each other in a second direction, and first main faces and second main faces opposing each other in a third direction, the ceramic element body having a longer side in the first direction; a first external electrode provided on the first end face, wrapping around a first ridge between the first end face and the first main face or the second main face, and covering a part of the first main face and a part of the second main face; a second external electrode provided on the second end face, wrapping around a second ridge between the second end face and the first main face or the second main face, and covering a part of the first main face and a part of the second main face; and a third external electrode provided on the first side face, wrapping around a third ridge between the first side face and the first main face or the second main face, and covering a part of the first main face and a part of the second main face. a first radius of curvature of the first external electrode at the first ridge portion and a second radius of curvature of the second external electrode at the second ridge portion are larger than a third radius of curvature of the third external electrode at the third ridge portion.

2. The ceramic part according to claim 1, wherein the ratio of the first radius of curvature and the second radius of curvature to the third radius of curvature is 1.1 or greater.

3. The ceramic part according to claim 1 or 2, wherein the radius of curvature of the first ridgeline portion and the radius of curvature of the second ridgeline portion in the ceramic body are smaller than the radius of curvature of the third ridgeline portion.

4. A ceramic part according to claim 1 or 2, wherein the first external electrode, the second external electrode and the third external electrode are made of a metal sintered body.

5. The ceramic part according to claim 1 or 2, further comprising a fourth external electrode provided on the second side surface, wrapping around a fourth ridge portion between the second side surface and the first main surface or the second main surface, and covering a part of the first main surface and a part of the second main surface, wherein the first radius of curvature and the second radius of curvature are larger than a fourth radius of curvature of the fourth external electrode at the fourth ridge portion.

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