Method for manufacturing chip type electronic component

Abstract

To provide a method for manufacturing chip type electronic components that effectively suppresses the occurrence of cracks originating from the surface of a base.SOLUTION: The method for manufacturing chip-type electronic components comprises a polishing step S03 for polishing the surface of a base 3 composed of a dielectric layer 6 primarily consisting of BaTiO3. In the polishing process S03, wet barrel polishing is performed using mullite 22.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a chip-type electronic component. [Background technology]

[0002] A known conventional chip-type electronic component includes a ceramic body and a pair of external electrodes provided on each of a pair of end faces of the ceramic body (see, for example, Patent Document 1). Within the body of the chip-type electronic component of Patent Document 1, multiple dielectric layers and multiple internal electrodes are alternately stacked. Ends of the multiple internal electrodes are exposed from the end faces of the body and are electrically connected to the external electrodes.

[0003] When manufacturing chip-type electronic components, a laminate is first formed by alternately stacking ceramic green sheets containing a dielectric material and ceramic green sheets on which internal electrodes have been formed by printing or the like. The laminate is then cut to obtain green chips, which are then fired to obtain an element body. After forming the element body, the end faces of the element body are polished by barrel polishing so that the ends of the internal electrodes are exposed from the end faces of the element body. External electrodes are then formed on the end faces of the element body by plating or the like, thereby obtaining a chip-type electronic component. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-163062 Summary of the Invention [Problem to be solved by the invention]

[0005] When the end faces of an element body are polished by barrel polishing, the surface of the element body may be scratched. Furthermore, depending on the components of the abrasives used in barrel polishing, for example, when external electrodes are baked onto the end faces of the element body, the main component of the dielectric layer constituting the element body may react with the components of the abrasives on the surface of the element body, resulting in a decrease in the toughness of the surface of the element body. In either case, this can lead to the occurrence of cracks originating on the surface of the element body. Therefore, in order to ensure the reliability of chip-type electronic components, a technology that can suppress the occurrence of such cracks is desired.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a method for manufacturing chip-type electronic components that can effectively suppress the occurrence of cracks that originate on the surface of the element body. [Means for solving the problem]

[0007] The gist of the present disclosure is as follows.

[0008] [1] A method for manufacturing chip-type electronic components, comprising a polishing step of polishing the surface of an element body including a dielectric layer whose main component is BaTiO3, wherein the polishing step involves wet barrel polishing using mullite.

[0009] In this method for manufacturing chip-type electronic components, wet barrel polishing is performed using mullite in the polishing step for polishing the surface of the element body. Mullite is a compound of aluminum oxide and silicon dioxide. It is harder than BaTiO3 but less hard than alumina and silicon carbide, which are widely used in wet barrel polishing. Therefore, wet barrel polishing using mullite polishes and smooths the surface of the element body while preventing scratches on the surface. Furthermore, because mullite is a compound of aluminum oxide and silicon dioxide, it is a chemically stable substance compared to alumina. Therefore, even if mullite remains on the surface of the element body after polishing, BaTiO3, the main component of the dielectric layer, is prevented from reacting with mullite on the surface of the element body during subsequent processes such as baking external electrodes, thereby preventing a decrease in the toughness of the surface of the element body. As a result, this method for manufacturing chip-type electronic components effectively prevents the occurrence of cracks originating from the surface of the element body.

[0010] [2] The method for manufacturing chip-type electronic components according to [1], wherein a solvent primarily composed of water is used in the wet barrel polishing. Using a solvent primarily composed of water more reliably prevents the surface of the element from being damaged during wet barrel polishing. Furthermore, it also more reliably prevents substances originating from the solvent from remaining on the surface of the element after polishing, thereby more reliably preventing a decrease in the toughness of the surface of the element due to a reaction between BaTiO3, the main component of the dielectric layer, and the remaining substances.

[0011] [3] The method for producing a chip-type electronic component according to [1] or [2], wherein silicon dioxide is used together with the mullite in the wet barrel polishing, which can further effectively suppress the occurrence of cracks originating from the surface of the element body.

[0012] [4] The method for producing a chip-type electronic component according to [1] or [2], wherein a compound containing potassium is used together with the mullite in the wet barrel polishing, which can further effectively suppress the occurrence of cracks originating from the surface of the element body.

[0013] [5] The method for producing a chip-type electronic component according to [1] or [2], wherein a compound containing sodium is used together with the mullite in the wet barrel polishing, which can further effectively suppress the occurrence of cracks originating from the surface of the element body. [Effects of the Invention]

[0014] According to the present disclosure, the occurrence of cracks originating from the surface of the element body can be suitably suppressed. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing a chip-type electronic component according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic vertical cross-sectional view of a chip-type electronic component. [Figure 3] FIG. 1 is a schematic cross-sectional view of a chip-type electronic component. [Figure 4] 1 is a flowchart showing an example of a method for manufacturing a chip-type electronic component. [Figure 5] FIG. 1 is a schematic perspective view showing an example of a crack that can occur in a general chip-type electronic component and originates from the surface of the element body. [Figure 6] FIG. 1(a) is a schematic diagram showing the wet barrel polishing process, and FIG. 1(b) is a schematic diagram showing the configuration of the media and abrasive material. [Figure 7] 10A and 10B are diagrams showing evaluation test results of a method for manufacturing a chip-type electronic component according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a preferred embodiment of a method for manufacturing a chip-type electronic component according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0017] FIG. 1 is a perspective view showing a chip-type electronic component according to an embodiment of the present disclosure. FIG. 2 is a schematic longitudinal cross-sectional view thereof, and FIG. 3 is a schematic transverse cross-sectional view thereof. The chip-type electronic component 1 shown in FIGS. 1 to 3 is exemplified by a multilayer ceramic capacitor 2. The multilayer ceramic capacitor 2 is configured to include an element body 3, multiple internal electrodes 4 (see FIGS. 2 and 3), and a pair of external electrodes 5. In the following description, for convenience, a first direction D1, a second direction D2, and a third direction D3 that are orthogonal to each other are defined. The first direction D1 corresponds to the length direction of the element body 3, the second direction D2 corresponds to the width direction of the element body 3, and the third direction D3 corresponds to the height direction of the element body 3.

[0018] The element body 3 has, for example, a rectangular parallelepiped shape. Rectangular parallelepiped shapes include shapes in which corners and ridges are chamfered and shapes in which corners and ridges are rounded. The element body has a pair of end faces 3a, a pair of side faces 3b, and a pair of side faces 3c. In this embodiment, the pair of end faces 3a are faces in the length direction of the element body 3 and face each other in the first direction D1. The pair of side faces 3b and the pair of side faces 3c extend so as to connect the pair of end faces 3a. The pair of side faces 3b are faces in the width direction of the element body 3 and face each other in the second direction D2. The pair of side faces 3c are faces in the height direction of the element body 3 and face each other in the third direction D3.

[0019] The length of the element body 3 is, for example, 0.4 mm or more and 7.5 mm or less. The width of the element body 3 is, for example, 0.2 mm or more and 6.3 mm or less. The height of the element body 3 is, for example, 0.2 mm or more and 2.8 mm or less. As an example, in this embodiment, the length of the element body 3 is 3.2 mm, the width of the element body 3 is 1.6 mm, and the height of the element body 3 is 1.6 mm.

[0020] The element body 3 is configured by stacking multiple dielectric layers 6. In this embodiment, the multiple dielectric layers 6 are dielectric layers primarily composed of BaTiO3 and are stacked in the third direction D3. Each dielectric layer 6 is configured, for example, from a sintered ceramic green sheet. The ceramic green sheet is configured, for example, by including a dielectric material. Examples of the dielectric material include BaTiO3-based, Ba(Ti,Zr)O3-based, (Ba,Ca)TiO3-based, and (Ba,Ca)(Ti,Zr)O3-based dielectric ceramics. The main component of the dielectric material primarily composed of BaTiO3 may have a perovskite structure. Preferably, Ba occupies 80% or more of the A site of the perovskite structure by molar ratio, and Ti occupies 80% or more of the B site of the perovskite structure by molar ratio. In the element body 3, the dielectric layers 6 are integrated to the extent that their boundaries are indiscernible.

[0021] The internal electrodes 4 are internal conductors arranged within the element body 3. The internal electrodes 4 are alternately stacked with the dielectric layers 6 in the third direction D3. Examples of conductive materials that constitute the internal electrodes 4 include Cu and Ni. In this embodiment, which uses the dielectric layers 6 mainly composed of BaTiO3, it is preferable to use Ni as the conductive material that constitutes the internal electrodes 4. The internal electrodes 4 may be composed of the same conductive material as the conductive material contained in the external electrodes 5. The internal electrodes 4 may be composed of a conductive material different from the conductive material contained in the external electrodes 5. The internal electrodes 4 are composed of a sintered body of a conductive paste containing the above-mentioned conductive material.

[0022] 2 and 3, the internal electrode 4 includes an internal electrode 4A extending to one of the pair of end faces 3a and an internal electrode 4B extending to the other of the pair of end faces 3a. The internal electrodes 4A and 4B are alternately arranged in the third direction D3.

[0023] The internal electrode 4A has a main electrode portion 4Aa and an extraction electrode portion 4Ab. When viewed from the third direction D3, the main electrode portion 4Aa has a rectangular shape that is, for example, slightly smaller than the element body 3. The extraction electrode portion 4Ab has a width smaller than that of the main electrode portion 4Aa and extends toward one of the pair of end faces 3a. An end of the extraction electrode portion 4Ab is exposed at one of the pair of end faces 3a and is electrically connected to one of the pair of external electrodes 5.

[0024] The internal electrode 4B has a main electrode portion 4Ba and an extraction electrode portion 4Bb. When viewed from the third direction D3, the main electrode portion 4Ba has, for example, a rectangular shape with the same dimensions as the main electrode portion 4Aa and overlaps with the main electrode portion 4Aa with the dielectric layer 6 sandwiched therebetween. The extraction electrode portion 4Bb has a width smaller than that of the main electrode portion 4Ba and extends toward the other of the pair of end faces 3a. An end of the extraction electrode portion 4Bb is exposed at the other of the pair of end faces 3a and is electrically connected to the other of the pair of external electrodes 5.

[0025] In this embodiment, in the element body 3, the portion where the internal electrodes 4 overlap in the third direction D3 is referred to as the capacitance-forming portion 3A, and the portion where the internal electrodes 4 do not overlap in the third direction D3 is referred to as the gap portion 3B (see FIGS. 2 and 3). The capacitance-forming portion 3A is a portion where the main electrode portion 4Aa of the internal electrode 4A and the main electrode portion 4Ba of the internal electrode 4B are located when viewed from the third direction D3, and is located inside the element body 3. The gap portion 3B is a portion where the main electrode portion 4Aa of the internal electrode 4A and the main electrode portion Ba of the internal electrode 4B are not located when viewed from the third direction, and is located on the surface side of the element body 3 so as to surround the capacitance-forming portion 3A.

[0026] The external electrode 5 is an external conductor disposed outside the element body 3. The external electrode 5 includes an external electrode 5A that covers one of the pair of end faces 3a, and an external electrode 5B that covers the other of the pair of end faces 3a (see FIGS. 2 and 3). A portion of the external electrode 5A may extend from one of the pair of end faces 3a onto each of the pair of side faces 3b and the pair of side faces 3c. Similarly, a portion of the external electrode 5B may extend from the other of the pair of end faces 3a onto each of the pair of side faces 3b and the pair of side faces 3c.

[0027] As shown in Figures 2 and 3, each of the external electrodes 5A and 5B includes a first electrode layer 5a and a second electrode layer 5b. In the example of Figures 2 and 3, in each of the external electrodes 5A and 5B, the portion covering the end face 3a and the portion extending around to the side faces 3b and 3c include the first electrode layer 5a and the second electrode layer 5b. The first electrode layer 5a is the inner layer (on the element body 3 side), and the second electrode layer 5b is the outer layer (on the opposite side from the element body 3). In this embodiment, the second electrode layer 5b constitutes the outermost layer of the external electrode 5.

[0028] The first electrode layer 5a is formed, for example, by baking a conductive paste applied to the surface of the element body 3. The conductive paste includes, for example, a resin, a plurality of glass particles, a plurality of metal particles, and an organic solvent. The resin includes, for example, an acrylic resin or ethyl cellulose. The plurality of metal particles include, for example, Cu particles or Ni particles.

[0029] The second electrode layer 5b is a plating layer formed on the first electrode layer 5a by, for example, a plating method. In this embodiment, the second electrode layer 5b is formed so as to cover the entire first electrode layer 5a. The second electrode layer 5b may be a Ni plating layer. The second electrode layer 5b may include a Ni plating layer and a Sn plating layer formed on the Ni plating layer.

[0030] Next, a method for manufacturing the above-mentioned chip-type electronic component 1 will be described.

[0031] Fig. 4 is a flowchart showing an example of a method for manufacturing the chip-type electronic component 1. As shown in Fig. 4, the method for manufacturing the chip-type electronic component 1 includes a laminating step S01, a firing step S02, a polishing step S03, and an electrode forming step S04.

[0032] The lamination step S01 is a step of forming green chips that will serve as the base of the element body 3. In the lamination step S01, ceramic green sheets that will become the dielectric layers 6, ceramic green sheets on which the patterns of the internal electrodes 4A are printed using a conductive paste, and ceramic green sheets on which the patterns of the internal electrodes 4B are printed using a conductive paste are prepared. Next, these green sheets are laminated in a predetermined order to form a laminate. The formed laminate is cut to obtain green chips that will serve as the base of the element body 3.

[0033] The firing step S02 is a step of firing the green chip to obtain the element body 3. In the firing step S02, the obtained green chip is fired at a predetermined temperature to obtain the element body 3. After the firing step S02, an annealing treatment may be performed in order to diffuse oxygen into the element body 3.

[0034] The polishing step S03 is a step of polishing the surface of the element body 3. In the polishing step S03, the surface of the element body 3 is polished by, for example, barrel polishing, to expose the internal electrodes 4 from a pair of end faces 3a of the element body 3. In the polishing step S03, the lead electrode portion 4Ab of the internal electrode 4A is exposed from one of the pair of end faces 3a of the element body 3, and the lead electrode portion 4Bb of the internal electrode 4B is exposed from the other of the pair of end faces 3a of the element body 3.

[0035] In this embodiment, wet barrel polishing is performed as the barrel polishing. In wet barrel polishing, a sealed rotary pot made of a material such as polyethylene is used. A plurality of element bodies 3 are placed in the sealed rotary pot together with a solvent, media, abrasives, etc., and the sealed rotary pot is rotated (see FIG. 6). This polishes the surfaces of the element bodies 3, exposing the internal electrodes 4 from a pair of end faces 3a of the element bodies 3. In addition, the corners of the element bodies 3 are chamfered, giving the element bodies 3 a rounded shape.

[0036] The electrode formation step S04 is a step of forming external electrodes 5 on the ends of the element body 3. In the electrode formation step S04, a conductive paste containing, for example, a metal powder mainly composed of Cu is prepared. Next, the ends of the element body 3 on the pair of end faces 3a side are each immersed in the conductive paste, and a paste layer is formed on the end. The paste layer is then heat-treated at a predetermined temperature to form a first electrode layer 5a. After the first electrode layer 5a is formed, a Ni plating layer is deposited on the first electrode layer 5a by, for example, a plating method, to form a second electrode layer 5b. Furthermore, if necessary, a Sn plating layer is further formed on the Ni plating layer. This results in the chip-type electronic component 1 shown in FIGS. 1 to 3.

[0037] FIG. 5 is a perspective view schematically showing the appearance of a typical chip-type electronic component 101 obtained by the manufacturing process described above. For convenience, FIG. 5 shows the element body 3 from one of a pair of end faces 3a with the external electrodes 5 removed. When observing the appearance of a typical chip-type electronic component 1 after manufacturing, as shown in FIG. 5, cracks K may have occurred in the element body 3, originating from small chips or the like present on the surface of the element body 3. If such cracks K originating on the surface of the element body 3 progress to the surface or inside of the element body 3, this may lead to a decrease in the reliability of the product.

[0038] To address these issues, in the method for manufacturing a chip-type electronic component according to this embodiment, wet barrel polishing is performed using mullite in the polishing step S03 described above, which polishes and smoothes the surface of the element body 3 and prevents the surface of the element body 3 from being scratched, thereby suppressing the occurrence of cracks K originating from the surface of the element body 3. More specifically, in the polishing step S03, as shown in FIG. 6(a), a plurality of element bodies 3 are placed in a sealed rotating pot 11 together with a solvent 12, media 13, abrasive 14, etc., and the sealed rotating pot 11 is rotated. The rotation speed of the sealed rotating pot 11 can be, for example, 50 rpm to 300 rpm.

[0039] The solvent 12 can be, for example, water as a main component. The solvent 12 may contain a surfactant, if necessary. The total weight of the element 3 per liter of the solvent 12 is set to, for example, 1 kg or less. The total weight of the media 13 per liter of the solvent 12 is set to, for example, 0.2 kg to 1 kg. The total weight of the abrasive 14 per liter of the solvent 12 is set to, for example, 30 g to 200 g.

[0040] Typical materials for the media 13 and abrasive 14 include alumina (Al2O3) and silicon carbide (SiC), but in this embodiment, wet barrel polishing is performed using mullite (Al-Si-O). Mullite is a compound of aluminum oxide and silicon dioxide, with the chemical formula 3Al2O3·2SiO2. Mullite is a substance with lower hardness than alumina and silicon carbide. Mullite may also be used with at least one of silicon oxide (SiO2), a compound containing potassium (K), or a compound containing sodium (Na).

[0041] Mullite may be contained in either the media 13 or the abrasive 14, or in both the media 13 and the abrasive 14. As shown in FIG. 6(b), the media 13 can be formed into a spherical shape by, for example, solidifying mullite powder with a resin. In the example of FIG. 6(b), the media 13 contains mullite 22 as a main component in a resin 21, and further contains particles 23 such as silicon oxide, a compound containing potassium, a compound containing sodium, or other additives 24. The diameter of the media 13 is, for example, approximately 0.5 mm to 3.0 mm. Although not shown, the abrasive 14 can also have a similar configuration to the media 13. The diameter of the abrasive 14 is smaller than that of the media 13, for example, approximately 0.1 μm to 100 μm.

[0042] As described above, in this method for manufacturing chip-type electronic components, wet barrel polishing is performed using mullite in the polishing step S03 for polishing the surface of the element body 3. Mullite is a compound of aluminum oxide and silicon dioxide, and is a substance that is harder than BaTiO3, but is less hard than alumina, silicon carbide, and other substances that are widely used in wet barrel polishing. Therefore, by performing wet barrel polishing using mullite, the surface of the element body is polished to a smooth finish, and scratches on the surface of the element body 3 can be prevented.

[0043] Furthermore, mullite is a compound of aluminum oxide and silicon dioxide, and is therefore a chemically stable substance compared to alumina. Therefore, even if mullite remains on the surface of the element body 3 after polishing, BaTiO3, the main component of the dielectric layer 6, is prevented from reacting with mullite on the surface of the element body 3 during subsequent baking of the external electrode 5 (first electrode layer 5a), and a decrease in the toughness of the surface of the element body 3 can be avoided. As described above, this method for manufacturing a chip-type electronic component can effectively prevent the occurrence of cracks K originating from the surface of the element body 3.

[0044] In this embodiment, a solvent containing water as its main component is used in the wet barrel polishing. By using a solvent containing water as its main component, it is possible to more reliably prevent the surface of the element body 3 from being damaged during the wet barrel polishing. Furthermore, it is possible to prevent substances resulting from the components of the solvent from remaining on the surface of the element body 3 after polishing, and it is possible to more reliably prevent a decrease in the toughness of the surface of the element body 3 due to a reaction between BaTiO3, the main component of the dielectric layer 6, and the remaining substances.

[0045] This embodiment includes a mode in which silicon dioxide is used together with mullite during wet barrel polishing. This embodiment also includes a mode in which a potassium-containing compound is used together with mullite, and a mode in which a sodium-containing compound is used together with mullite during wet barrel polishing. This further effectively suppresses the occurrence of cracks K originating from the surface of the element body 3.

[0046] [Example] Hereinafter, examples of the present disclosure will be described.

[0047] First, a green chip was formed as the base material of the element using a dielectric layer made of barium titanate (BaTiO3) doped with yttrium (Y), magnesium (Mg), manganese (Mn), vanadium (V), calcium (Ca), and silicon (Si), and an internal electrode made of nickel. Next, this green chip was placed in an atmosphere with an oxygen partial pressure of 1 × 10 -12 The element was held at 1250°C for two hours under a low oxygen partial pressure of 1 atm, and then fired at a temperature increase / decrease rate of 200°C / h to obtain an element body. The element body was then held at 1050°C for two hours while nitrogen gas bubbling in 20°C water was passed through, and annealed at a temperature increase / decrease rate of 200°C / h to produce multiple element samples measuring 3.2mm x 2.5mm x 2.5mm. The internal electrodes were 1μm thick, and the dielectric layers were 4μm thick. The number of dielectric layers was 420.

[0048] Next, each of the prepared samples was subjected to wet barrel polishing. In wet barrel polishing, the element body was placed in a sealed rotating pot along with a solvent, media, abrasives, etc., and the sealed rotating pot was rotated to polish the surface of the element body so that the lead electrode portions of the internal electrodes were exposed from a pair of end faces of the element body. The rotation speed of the sealed rotating pot was 100 rpm. A sealed rotating pot with a capacity of 1 liter was used. The total weight of the element body per liter of solvent was 0.5 kg, and the total weight of the media was 0.5 kg. The total weight of the abrasives per liter of solvent was 75 g.

[0049] Fig. 7 shows the results of the evaluation test. As shown in Fig. 7, in Comparative Examples 1 to 5, mullite was not used as either the media or the abrasive, and in Examples 1 to 6, mullite was used as either the media or the abrasive. Comparative Example 1 was a case in which no solvent, media, or abrasive was used. In Comparative Examples 2 to 5 and Examples 1 to 6, water was used as the solvent. In Comparative Examples 2 to 4 and Examples 4 to 6, yttrium-stabilized zirconia was used as the media, and in Examples 2 and 3, mullite was used as the media. In Comparative Example 5, an Al2O3-SiO2 ceramic was used as the media. The diameter of the media was 1 mm in all cases.

[0050] In Comparative Example 2, Al2O3 was used as the abrasive, and in Comparative Example 3, a material containing Al2O3 and SiO2 was used as the abrasive. The mass ratios of Al2O3 and SiO2 were 50% and 50%, respectively. In Comparative Examples 4 and 5, SiC was used as the abrasive. In Examples 1 and 3, mullite was used as the abrasive. In Example 2, no abrasive was used. In Example 4, a material containing mullite and SiO2 was used as the abrasive. The mass ratios of mullite and SiO2 were 90% and 10%, respectively. In Example 5, a material containing mullite, SiO2, and K2CO3 was used as the abrasive. The mass ratios of mullite, SiO2, and K2CO3 were 86%, 10%, and 4%, respectively. In Example 6, a material containing mullite, SiO2, K2CO3, and Na2CO3 was used as the abrasive. The mass ratios of mullite, SiO2, K2CO3, and Na2CO3 were 86%, 10%, 2%, and 2%, respectively. The diameter of the abrasive was set to about 0.5 μm to 2 μm. The mass ratio of mullite in the abrasive is preferably 80% or more and 90% or less.

[0051] In Examples 1 to 6, the surface roughness Ra of the element body in each sample was 0.075 μm or less. In particular, in Examples 5 and 6, the surface roughness Ra of the element body in each sample was 0.005 μm or less. On the other hand, in Comparative Examples 1 to 5, the surface roughness Ra of the element body in each sample exceeded 0.07 μm. In addition, in Examples 1 to 6, the surface roughness RSm of the element body in each sample was 3.0 μm or more and 7.0 μm or less. In particular, in Examples 5 and 6, the surface roughness RSm of the element body in each sample was 4.0 μm or more and 6.0 μm or less. On the other hand, in Comparative Examples 1 to 5, the surface roughness RSm of the element body in each sample was less than 3.0 μm or more than 7.0 μm.

[0052] The definitions of surface roughness Ra and surface roughness RSm follow JIS B 0601:2013. Surface roughness Ra is a parameter that represents the arithmetic mean roughness of the profile over a reference length. Surface roughness RSm is a parameter that represents the average length of the profile over a reference length.

[0053] After wet barrel polishing was performed under the conditions of Comparative Examples 1 to 5 and Examples 1 to 6, a pressure cooker test (hereinafter referred to as "PCT") was performed on each sample. The number of samples in each of Comparative Examples 1 to 5 and Examples 1 to 6 was 20. The test conditions were 121°C and 95% RH. The cumulative test times were 10 hours, 24 hours, 100 hours, and 240 hours. After each time had elapsed, the appearance of each sample was observed with a stereomicroscope, and the presence or absence of cracks originating from the surface of the element body was counted.

[0054] As shown in FIG. 7, in all of Comparative Examples 1 to 5, cracks originating from the surface of the element body occurred when the PCT test time was 10 hours. On the other hand, in all of Examples 1 to 6, cracks originating from the surface of the element body did not occur when the PCT test time was 10 hours. In Examples 4 to 6, the time until cracks occurred was even longer, and no cracks originating from the surface of the element body occurred even when the PCT test time was 24 hours. In Example 5, no cracks originating from the surface of the element body occurred even when the PCT test time was 100 hours, and in Example 6, no cracks originating from the surface of the element body occurred even when the PCT test time was 240 hours.

[0055] From the above results, it was confirmed that the method of performing wet barrel polishing using mullite as disclosed herein can effectively suppress the occurrence of cracks originating from the surface of the element body in chip-type electronic components. [Explanation of symbols]

[0056] 1...Chip-type electronic component, 2...Multilayer ceramic capacitor (chip-type electronic component), 3...Element body, 12...Solvent, 22...Mullite, 23...Particles (silicon dioxide), 24...Additives (compounds containing potassium, compounds containing sodium).

Claims

1. BaTiO ３ a polishing step of polishing a surface of an element body including a dielectric layer mainly composed of In the polishing step, wet barrel polishing is performed using mullite.

2. 2. The method for producing chip-type electronic components according to claim 1, wherein a solvent containing water as a main component is used in the wet barrel polishing.

3. 3. The method for producing a chip-type electronic component according to claim 1, wherein silicon dioxide is used together with the mullite in the wet barrel polishing.

4. 3. The method for producing a chip-type electronic component according to claim 1, wherein a compound containing potassium is used together with the mullite in the wet barrel polishing.

5. 3. The method for producing a chip-type electronic component according to claim 1, wherein a compound containing sodium is used together with the mullite in the wet barrel polishing.

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