Electronic component and film forming method

Abstract

The invention relates to an electronic component and a film forming method. The electronic component is provided with a base body (20) and an aluminum oxide film (50) covering the outer surface (21) of the base body (20). The aluminum oxide film (50) has a film-like portion (51) made of aluminum oxide and in contact with the outer surface (21) of the base (20), and a particle layer (52) located on the outer surface side of the film-like portion (51). The particle layer (52) contains a plurality of aluminum oxide particles (53) bonded to the outer surface of the film-like part (51). The average thickness of the alumina film (50) including the film-like portion (51) and the particle layer (52) is 0.05 [mu] m or more and 2.0 [mu] m or less. The distance (P) between the particles (53) is 1.3 [mu] m or less.

Description

Technical Field

[0001] The present disclosure relates to an electronic component and a film forming method. Background Art

[0002] The invention described in Patent Document 1 comprises a substrate, an internal electrode, an external electrode and a protective film. The internal electrode is located inside the substrate. The protective film covers the outer surface of the substrate. The protective film is an aluminum oxide film. The thickness of the protective film is 0.05 μm to 2 μm. The external electrode is stacked on the outer surface of the protective film. In addition, the external electrode is electrically connected to the internal electrode.

[0003] Patent Document 1: Japanese Patent No. 4637440 Summary of the invention

[0004] In the protective film described in Patent Document 1, the thinner the film thickness, the lower the barrier property of the protective film. On the other hand, when the film thickness is increased in order to ensure the barrier property, the stress of the protective film increases. Then, when the stress of the protective film is large, when an external force is applied to the protective film, cracks may be generated in the protective film due to the external force. Therefore, a technology that can suppress cracks in the protective film and increase the film thickness of the protective film is desired.

[0005] In order to solve the above-mentioned problems, one method of the present invention is an electronic component, comprising a substrate and an aluminum oxide film covering the outer surface of the substrate, the aluminum oxide film having a film-like portion made of aluminum oxide in contact with the outer surface of the substrate, and a particle layer located on the outer surface side of the film-like portion, the particle layer comprising a plurality of aluminum oxide particles bonded to the outer surface of the film-like portion, the aluminum oxide film including the film-like portion and the particle layer has an average thickness of not less than 0.05 μm and not more than 2.0 μm, and the spacing between the particles is not more than 1.3 μm.

[0006] In addition, in order to solve the above-mentioned problems, one embodiment of the present invention is a film-forming method, which forms an aluminum oxide film on the outer surface of a substrate, and comprises: a feeding step, in which the substrate is fed into a first chamber capable of heating the internal environment; an atomization step, in which a liquid raw material containing aluminum atoms and oxygen atoms is formed into a mist by using ultrasonic waves in a second chamber; a supply step, in which the atomized raw material is supplied from the second chamber to the first chamber together with a carrier gas; and a first heating step, in which the first chamber is heated to a first temperature while the supply step is performed, and a second heating step, which is performed after the first heating step, in which the first chamber is heated to a second temperature that is specified to be lower than the first temperature while the supply step is performed.

[0007] According to the above structure, the film thickness of the aluminum oxide film can be increased while suppressing the occurrence of cracks in the aluminum oxide film. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a three-dimensional diagram of electronic components.

[0009] Figure 2 is a side view of an electronic component.

[0010] Figure 3 It is along Figure 2 A cross-sectional view of line 3-3.

[0011] Figure 4 It is along Figure 2 End view of the aluminum oxide film near line 4-4.

[0012] Figure 5 It is the measurement result of the scratch strength test.

[0013] Figure 6 This is an explanatory diagram for explaining a method for manufacturing an electronic component.

[0014] Figure 7 This is an explanatory diagram for explaining a method for manufacturing an electronic component.

[0015] Figure 8 This is an explanatory diagram for explaining a method for manufacturing an electronic component.

[0016] Fig. 9 This is an explanatory diagram for explaining a method for manufacturing an electronic component. DETAILED DESCRIPTION

[0017] <One embodiment of electronic component>

[0018] Hereinafter, one embodiment of the electronic component will be described with reference to the accompanying drawings. In addition, the accompanying drawings may enlarge the components for easy understanding. The dimensional ratio of the components may be different from the actual ones or from those in other drawings.

[0019] <About electronic components>

[0020] like Figure 1As shown, the electronic component 10 is, for example, a surface-mounted negative characteristic thermistor component mounted on a circuit board or the like. In addition, the negative characteristic thermistor component has a characteristic that the resistance value decreases when the temperature rises. The electronic component 10 includes a substrate 20. The substrate 20 is substantially quadrangular and has a central axis CA. In addition, hereinafter, an axis extending along the central axis CA is set as a first axis X. In addition, one of the axes orthogonal to the first axis X is set as a second axis Y. Moreover, an axis orthogonal to the first axis X and the second axis Y is set as a third axis Z. In addition, one of the directions along the first axis X is set as a first positive direction X1, and the direction opposite to the first positive direction X1 in the direction along the first axis X is set as a first negative direction X2. In addition, one of the directions along the second axis Y is set as a second positive direction Y1, and the direction opposite to the second positive direction Y1 in the direction along the second axis Y is set as a second negative direction Y2. In addition, one of the directions along the third axis Z is set as a third positive direction Z1, and the direction opposite to the third positive direction Z1 in the direction along the third axis Z is set as a third negative direction Z2.

[0021] The outer surface 21 of the substrate 20 has six planes 22. In addition, the "surface" of the substrate 20 mentioned here refers to the part that can be observed as a surface when observing the substrate 20 as a whole. That is, for example, even if there are tiny bumps and steps that can only be understood by magnifying and observing a part of the substrate 20 with a microscope, it appears as a plane or a curved surface. The six planes 22 face different directions. The six planes 22 are roughly divided into a first end face 22A facing the first positive direction X1, a second end face 22B facing the first negative direction X2, and four side faces 22C. The four side faces 22C are respectively a face facing the third positive direction Z1, a face facing the third negative direction Z2, a face facing the second positive direction Y1, and a face facing the second negative direction Y2.

[0022] The arithmetic mean roughness (Ra) of the outer surface 21 of the substrate 20 is 0.5 μm or less. In addition, the arithmetic mean roughness of the outer surface 21 of the substrate 20 is measured by a laser microscope. For example, in the manufacturing process of the electronic component 10, when the outer surface 21 is exposed, a linear scan is performed at any part of the outer surface 21 and a length of 300 μm or more is measured.

[0023] In addition, the boundary portion between two adjacent planes 22 and the boundary portion between three adjacent planes 22 in the outer surface 21 of the base body 20 are curved surfaces. That is, the corners of the base body 20 are so-called rounded.

[0024] like Figure 2 As shown, the dimension of the substrate 20 along the first axis X is greater than the dimension along the third axis Z. Figure 1As shown, the dimension of the substrate 20 along the first axis X is greater than the dimension along the second axis Y. The material of the substrate 20 is a semiconductor. Specifically, the material of the substrate 20 is a ceramic formed by firing a metal oxide containing at least one of Mn, Fe, Ni, Co, Ti, Ba, Al and Zn as a component.

[0025] like Figure 3 As shown, the electronic component 10 includes two first internal electrodes 41 and two second internal electrodes 42 . The first internal electrodes 41 and the second internal electrodes 42 are located inside the base body 20 .

[0026] The material of the first internal electrode 41 is a conductive material. For example, the material of the first internal electrode 41 is palladium. The material of the second internal electrode 42 is the same as that of the first internal electrode 41.

[0027] The first internal electrode 41 has a rectangular plate shape. The main surface of the first internal electrode 41 is perpendicular to the second axis Y. The second internal electrode 42 has the same rectangular plate shape as the first internal electrode 41 . The main surface of the second internal electrode 42 is perpendicular to the second axis Y as the first internal electrode 41 .

[0028] The dimension of the first internal electrode 41 along the direction of the first axis X is smaller than the dimension of the base body 20 along the direction of the first axis X. Figure 1 As shown, the dimension of the first inner electrode 41 along the third axis Z is approximately two thirds of the dimension of the base body 20 along the third axis Z. The dimensions of the second inner electrode 42 in each direction are the same as those of the first inner electrode 41 .

[0029] like Figure 3 As shown in FIG. 2 , the first internal electrode 41 and the second internal electrode 42 are located at different positions in the direction along the second axis Y. That is, from the side surface 22C facing the second positive direction Y1 toward the second negative direction Y2, a total of four internal electrodes are alternately arranged in the order of the first internal electrode 41, the second internal electrode 42, the first internal electrode 41, and the second internal electrode 42. In the present embodiment, the distances between the internal electrodes in the direction along the second axis Y are equal.

[0030] like Figure 1 As shown in FIG. 1 , the two first internal electrodes 41 and the two second internal electrodes 42 are both located at the center of the substrate 20 along the direction of the third axis Z. Figure 3 As shown, the first internal electrode 41 is located near the first positive direction X1, and the second internal electrode 42 is located near the first negative direction X2.

[0031] Specifically, the end of the first internal electrode 41 on the first positive direction X1 side coincides with the end of the base 20 on the first positive direction X1 side. The end of the first internal electrode 41 on the first negative direction X2 side is located inside the base 20 and does not reach the end of the base 20 on the first negative direction X2 side. On the other hand, the end of the second internal electrode 42 on the first negative direction X2 side coincides with the end of the base 20 on the first negative direction X2 side. The end of the second internal electrode 42 on the first positive direction X1 side is located inside the base 20 and does not reach the end of the base 20 on the first positive direction X1 side.

[0032] like Figure 3 As shown, the electronic component 10 includes an aluminum oxide film 50. The aluminum oxide film 50 covers the outer surface 21 of the substrate 20. In the present embodiment, the aluminum oxide film 50 covers the entire area of ​​the outer surface 21 of the substrate 20. In addition, in the present embodiment, the aluminum oxide film 50 means that the main component of the film is aluminum oxide. Specifically, the aluminum oxide film 50 is a film in which the total atomic percentage of aluminum atoms and oxygen atoms contained in the film is 80% or more. In addition, in the present embodiment, the aluminum oxide film 50 contains hydrogen atoms and carbon atoms.

[0033] The electronic component 10 includes a first external electrode 61 and a second external electrode 62. The first external electrode 61 is located on the outer surface of the aluminum oxide film 50. The first external electrode 61 includes a first base electrode 61A and a first metal layer 61B. The first base electrode 61A is stacked on a portion of the outer surface 21 of the substrate 20 including the first end surface 22A from above the aluminum oxide film 50. The first base electrode 61A is a five-sided electrode covering a portion of the first positive direction X1 side of the first end surface 22A and four side surfaces 22C of the substrate 20. In the present embodiment, the material of the first base electrode 61A is copper and glass. In addition, the first base electrode 61A is a sintered body.

[0034] like Figure 3 As shown in FIG. 1 , the first metal layer 61B covers the first base electrode 61A from the outside. Therefore, the first metal layer 61B is stacked on the first base electrode 61A. In addition, a portion of the first metal layer 61B protrudes from the first base electrode 61A. That is, a portion of the outer edge of the first metal layer 61B directly covers the aluminum oxide film 50 without the first base electrode 61A. Although not shown in the figure, the first metal layer 61B has a two-layer structure of a nickel layer and a tin layer in order from the first base electrode 61A side.

[0035] The second external electrode 62 includes a second base electrode 62A and a second metal layer 62B. The second base electrode 62A is laminated on a portion of the outer surface 21 of the substrate 20 including the second end surface 22B from above the aluminum oxide film 50. The second base electrode 62A is a five-sided electrode that covers a portion of the second end surface 22B and four side surfaces 22C of the substrate 20 on the first negative direction X2 side. In this embodiment, the material of the second base electrode 62A is the same as that of the first external electrode 61, that is, copper and glass. In addition, the second base electrode 62A is a sintered body like the first base electrode 61A.

[0036] The second metal layer 62B covers the second base electrode 62A from the outside. Therefore, the second metal layer 62B is stacked on the second base electrode 62A. In addition, a part of the second metal layer 62B protrudes from the second base electrode 62A. That is, a part of the outer edge of the second metal layer 62B directly covers the aluminum oxide film 50 without the second base electrode 62A. Although not shown in the figure, the second metal layer 62B has a two-layer structure of a nickel layer and a tin layer in order from the second base electrode 62A side, similarly to the first metal layer 61B.

[0037] The second external electrode 62 does not reach the first external electrode 61 on the side surface 22C, but is arranged separately from the first external electrode 61 in the direction along the first axis X. Therefore, on the side surface 22C of the substrate 20, the first external electrode 61 and the second external electrode 62 are not stacked in the central portion along the direction of the first axis X, and the aluminum oxide film 50 is exposed. Figure 1 to Figure 3 In FIG. 1 , the first external electrode 61 and the second external electrode 62 are indicated by two-dot chain lines.

[0038] The first external electrode 61 is connected to the end of the first internal electrode 41 on the first positive direction X1 side via the first through portion 71 that penetrates the aluminum oxide film 50. Therefore, the first external electrode 61 is electrically connected to the first internal electrode 41. Although the details will be described later, the first through portion 71 is formed by extending the palladium constituting the first internal electrode 41 toward the first external electrode 61 side during the manufacturing process of the electronic component 10.

[0039] In addition, the second external electrode 62 is connected to the end of the second internal electrode 42 on the first negative direction X2 side via the second through portion 72 that penetrates the aluminum oxide film 50. Therefore, the second external electrode 62 is electrically connected to the second internal electrode 42. The second through portion 72 is also formed by extending the palladium constituting the second internal electrode 42 toward the second external electrode 62 side during the manufacturing process of the electronic component 10, similarly to the first through portion 71. Figure 3In the figure, the first internal electrode 41 and the first through-hole 71 are shown as different components with a boundary, but in fact there is no clear boundary between the two. This is also true for the second through-hole 72. Figure 1 In the figure, the first penetration portion 71 is omitted.

[0040] <About Alumina Film>

[0041] like Figure 4 As shown, the aluminum oxide film 50 has a film-like portion 51 and a particle layer 52. The film-like portion 51 is made of aluminum oxide. The film-like portion 51 is a portion where aluminum oxide exists without gaps when it moves on the outer surface 21 along the shape of the outer surface 21 of the substrate 20. The film-like portion 51 is in contact with the outer surface 21 of the substrate 20. More specifically, the film-like portion 51 covers the entire outer surface 21 of the substrate 20.

[0042] The particle layer 52 is located on the outer surface side relative to the film-like portion 51. The particle layer 52 includes a plurality of particles 53 made of aluminum oxide. The plurality of particles 53 are bonded to the outer surface of the film-like portion 51. Figure 4 In FIG. 5 , only a part of the particles 53 are marked with reference numerals. Figure 4 In the embodiment, a part of the particles 53 is separated from the membrane portion 51, but in Figure 4 When the end surface is observed while being offset in the depth direction of the paper surface in FIG.

[0043] Each particle 53 has various shapes. For example, assume that the aluminum oxide film 50 is observed end-on in a cross section perpendicular to any plane 22 of the substrate 20. In this case, the particle 53 has an elliptical shape or a plurality of particles 53 are connected to form a twisted shape.

[0044] The interval P between each particle 53 is less than 1.3 μm. In the present embodiment, the maximum length of the interval P between the particles 53 is 0.51 μm. The interval P between the particles 53 is measured as follows. First, a cross section that is orthogonal to any plane 22 of the substrate 20 and includes the aluminum oxide film 50 is photographed using an electron microscope. Next, for the captured image, an approximate straight line L1 is drawn relative to the outer surface 21. The approximate straight line L1 can be obtained, for example, by the least squares method. Then, the shortest distance between the particles 53 in a direction parallel to the approximate straight line L1 is taken as the interval P between the particles 53. In addition, in Figure 4 In the diagram, only the largest interval P is shown as a representative.

[0045] The average value of the thickness of the aluminum oxide film 50 including the film portion 51 and the particle layer 52 is greater than or equal to 0.05 μm and less than or equal to 2.0 μm. The average value of the thickness of the aluminum oxide film 50 is the sum of the average value of the thickness of the film portion 51 and the average value of the thickness of the particle layer 52. In the present embodiment, the average value of the thickness of the aluminum oxide film 50 is 0.57 nm.

[0046] The average thickness of the film portion 51 is 0.3 μm. The thickness of the film portion 51 refers to the shortest distance from the position of the film portion 51 on the outer surface 21 side of the base 20 to the outer surface of the film portion 51. The average thickness of the film portion 51 is measured as follows.

[0047] First, a cross section orthogonal to any plane 22 of the substrate 20 and including the aluminum oxide film 50 is photographed using an electron microscope. Next, for the photographed image, a range in the direction along the outer surface of the film-like portion 51 is determined. Within this range, for a measurement range of at least 5 μm or more, the cross-sectional area of ​​the film-like portion 51 is calculated by image processing. Then, the thickness of the film-like portion 51 in the cross section is calculated by dividing the calculated cross-sectional area of ​​the film-like portion 51 in the measurement range by the length of the measurement range. This is taken as the average value of the thickness of the film-like portion 51.

[0048] The average value of the thickness of the particle layer 52 is 0.27 μm. The average value of the thickness of the particle layer 52 is calculated as follows. A cross section orthogonal to any plane 22 of the substrate 20 and including the aluminum oxide film 50 is photographed using an electron microscope. Next, for the photographed image, a range in the direction along the outer surface of the membrane portion 51 is determined. Within this range, for a measurement range of at least 5 μm or more, the total cross-sectional area of ​​the particles 53 is calculated by image processing. Then, the thickness of the particle layer 52 in the cross section is calculated by dividing the total cross-sectional area of ​​the particles 53 in the calculated measurement range by the length of the measurement range. This is taken as the average value of the thickness of the particle layer 52. In addition, in the particle layer 52, in the measurement range, there are parts where the particles 53 exist and parts where the particles 53 do not exist. Moreover, in the parts where the particles 53 do not exist, the thickness of the particle layer 52 is locally zero. Therefore, the average value of the thickness of the particle layer 52 calculated by the above method becomes a value smaller than the particle size of each particle 53.

[0049] The average value of the thickness of the particle layer 52 is 20% to 70% of the average value of the thickness of the aluminum oxide film 50. Specifically, in this embodiment, the average value of the thickness of the particle layer 52 is about 47.4% of the average value of the thickness of the aluminum oxide film 50.

[0050] <About the scratch strength test of aluminum oxide film>

[0051] Here, a test was conducted to measure the scratch strength of the aluminum oxide film 50. In this test, the external force until the inside of the aluminum oxide film 50 is damaged when the outer surface of the aluminum oxide film 50 is scratched is regarded as the "scratch strength".

[0052] First, a plurality of samples were prepared. For each sample, an aluminum oxide film 50 including a film-like portion 51 and a particle layer 52 was formed on a silicon substrate. Then, for each sample, the thickness of the aluminum oxide film 50 was changed within a range of 0.05 μm to 0.95 μm.

[0053] In the scratch strength test, the sample is fixed on a workbench so that the probe is in close contact with the outer surface of the aluminum oxide film 50 of the sample. Then, the workbench on which the sample is fixed is moved at a constant speed while increasing the pushing strength of the probe on the aluminum oxide film 50. At this time, the pushing strength when a scratch such as a scratch that exposes the silicon substrate is generated inside the aluminum oxide film 50 is measured as the scratch strength.

[0054] like Figure 5 As shown in FIG. 1 , it is found that the scratch strength tends to increase as the thickness of the aluminum oxide film 50 decreases. In particular, when the thickness of the aluminum oxide film 50 exceeds about 0.2 μm, the scratch strength remains at a low level of approximately less than 20 mN. On the other hand, when the thickness of the aluminum oxide film 50 becomes about 0.2 μm or less, the scratch strength increases sharply as the thickness decreases. Therefore, it can be seen that from the viewpoint of preventing the occurrence of cracks, the thickness of the aluminum oxide film 50 is preferably 0.2 μm or less.

[0055] <Method for manufacturing electronic components>

[0056] Next, a method for manufacturing the electronic component 10 will be described.

[0057] like Figure 6 As shown, the method for manufacturing the electronic component 10 includes a laminate preparation step S11, a rounding step S12, an input step S13, an atomization step S14, a supply step S15, a first heating step S16, and a second heating step S17. In addition, the method for manufacturing the electronic component 10 also includes a conductor coating step S18, a curing step S19, and a plating step S20.

[0058] First, when forming the base 20, in the stack preparation step S11, a stack is prepared. The stack at this stage is in a state before rounding, and is in the shape of a rectangular parallelepiped with 6 planes 22. For example, first, a plurality of ceramic sheets that will become the base 20 are prepared. The sheet is in the shape of a thin plate. A conductive paste that will become the first internal electrode 41 is stacked on the sheet. A ceramic sheet that will become the base 20 is stacked on the stack paste. A conductive paste that will become the second internal electrode 42 is stacked on the sheet. In this way, ceramic sheets and conductive paste are stacked. Then, the stacked sheets are crimped in the stacking direction by means of mold stamping or the like. Then, the crimped sheets are cut into a specified size, thereby forming an unfired stack. Then, the unfired stack is fired at a high temperature, thereby preparing the stack.

[0059] Next, a chamfering process step S12 is performed. In the chamfering process step S12, the stacked body prepared in the stacked body preparation step S11 is chamfered. Through this process, the base body 20 with rounded corners is obtained.

[0060] Next, the charging step S13 to the second heating step S17 are sequentially performed. From the charging step S13 to the second heating step S17, the film forming apparatus 100 is used.

[0061] like Figure 7 As shown, the film forming apparatus 100 includes a first chamber 91. The first chamber 91 is capable of heating the internal environment. Specifically, the first chamber 91 includes a heater 91A, a container body 91B, and a discharge passage 91C. The heater 91A is located at the bottom of the container body 91B. By driving the heater 91A, the environment in the container body 91B is heated. The discharge passage 91C is connected to the container body 91B. The interior of the container body 91B is connected to the outside through the discharge passage 91C.

[0062] The film forming device 100 includes a second chamber 92, a liquid supply nozzle 93, and a gas supply nozzle 94. The second chamber 92 includes an ultrasonic generator 92A, a container body 92B, and a connecting passage 92C. The ultrasonic generator 92A is located at the bottom of the container body 92B. By driving the ultrasonic generator 92A, the liquid supplied to the inside of the container body 92B can be formed into a mist. The connecting passage 92C is connected to the container body 91B of the first chamber 91 and the container body 92B of the second chamber 92. That is, the container body 92B of the second chamber 92 is connected to the container body 91B of the first chamber 91 via the connecting passage 92C. The liquid supply nozzle 93 can supply a liquid raw material into the container body 92B. In addition, the gas supply nozzle 94 can supply a carrier gas into the container body 92B.

[0063] In addition, if Figure 6As shown, the input process S13 is performed. Figure 7 As shown, in the loading step S13, the substrate 20 is loaded into the first chamber 91 of the film forming apparatus 100. Then, the heater 91A of the first chamber 91 is driven to heat the environment in the first chamber 91.

[0064] Next, if Figure 6 As shown, the atomization step S14 is performed. Figure 8 As shown, in the atomization step S14, a liquid raw material is placed in the second chamber 92 via the liquid supply nozzle 93. In addition, the ultrasonic generator 92A is driven to form the raw material into a mist using ultrasonic waves. In addition, the mist means a state of droplets with a particle size of less than 10 μm. The raw material includes aluminum acetylacetonate, methanol and water. That is, the raw material includes aluminum atoms and oxygen atoms. In addition, the raw material includes carbon atoms and hydrogen atoms.

[0065] Next, if Figure 6 As shown, the supply process S15 is performed. Fig. 9 As shown, in the supply process S15, a carrier gas is supplied into the second chamber 92 via the gas supply nozzle 94. Thus, the mist-like raw material is supplied from the second chamber 92 into the first chamber 91 together with the carrier gas. The carrier gas is, for example, an inert gas such as oxygen, ozone, nitrogen, and argon. In addition, the carrier gas may also be a reducing gas such as hydrogen and a synthetic gas. In addition, the excess carrier gas and the excess raw material supplied into the first chamber 91 are discharged to the outside of the film forming apparatus 100 via the exhaust passage 91C.

[0066] Next, if Figure 6 As shown, the first heating step S16 is performed. In the first heating step S16, the environment in the first chamber 91 is heated while the supply step S15 is performed. Specifically, in the first heating step S16, the heater 91A is driven to heat the first chamber 91 to a first temperature. By heating, the particle size of the mist flowing from the second chamber 92 into the first chamber 91 is miniaturized. The temperature in the first chamber 91 at this time is, for example, several hundred degrees. In the first heating step S16, the mist-like raw material is supplied to the substrate 20 along with vaporization. As a result, a dense film-like portion 51 is formed on the outer surface 21 of the substrate 20.

[0067] Next, the second heating step S17 is performed. In the second heating step S17, after the first heating step S16, the first chamber 91 is heated to a second temperature that is specified to be lower than the first temperature while the supply step S15 is performed. The second temperature is, for example, a temperature that is about 100 degrees lower than the first temperature. In this way, in the second heating step S17, when the first chamber 91 is set to the second temperature, the particle size of the mist raw material becomes larger than that in the first heating step S16. That is, in the second heating step S17, the particle size of the mist in the first chamber 91 becomes larger than that in the first heating step S16. Such mist with a large particle size adheres to the membrane portion 51 to form particles 53. In this step, a plurality of particles 53 are formed in the membrane portion 51, forming a particle layer 52 that is a part of the aluminum oxide film 50.

[0068] In addition, during the execution of the above-mentioned atomization step S14, the supply step S15, the first heating step S16 and the second heating step S17, the composition ratio of atoms contained in the raw material is kept constant. That is, in any time period of the above-mentioned steps, the composition ratio of the mist formed by the raw material is substantially the same. These steps from the supply step S13 to the second heating step S17 are a film forming method for forming the aluminum oxide film 50 on the outer surface 21 of the substrate 20.

[0069] Next, the conductor coating step S18 is performed. In the conductor coating step S18, the conductor paste is applied to two places on the surface of the aluminum oxide film 50, including a part of the portion covering the first end face 22A of the substrate 20 and a part of the portion covering the second end face 22B of the substrate 20. Specifically, the conductor paste is applied to the aluminum oxide film 50 covering the entire area of ​​the first end face 22A and a part of the four side faces 22C. In addition, the conductor paste is applied to the aluminum oxide film 50 covering the entire area of ​​the second end face 22B and a part of the four side faces 22C.

[0070] Next, a curing step S19 is performed. Specifically, in the curing step S19, the base 20 is heated. In the curing step S19, the conductor paste applied in the conductor applying step S18 is fired to form the first base electrode 61A and the second base electrode 62A.

[0071] In the present embodiment, during heating in the curing step S19, due to the Kirkendall effect caused by the difference in diffusion speed between the first internal electrode 41 and the first base electrode 61A, palladium contained in the first internal electrode 41 side is attracted to the first base electrode 61A side containing copper. As a result, the first through portion 71 extends from the first internal electrode 41 toward the first base electrode 61A, penetrating the aluminum oxide film 50. As a result, the first internal electrode 41 is connected to the first base electrode 61A. In this regard, the second through portion 72 connecting the second internal electrode 42 to the second base electrode 62A is also the same.

[0072] Next, a plating step S20 is performed. Electroplating is performed on the first base electrode 61A and the second base electrode 62A. Thus, a first metal layer 61B is formed on the surface of the first base electrode 61A. In addition, a second metal layer 62B is formed on the surface of the second base electrode 62A. Although not shown in the figure, the first metal layer 61B and the second metal layer 62B are electroplated with nickel and tin to form a two-layer structure. In this way, the electronic component 10 is formed.

[0073] <Effects of the present embodiment>

[0074] (1) According to the above-mentioned embodiment, the thickness of the aluminum oxide film 50 as a whole is such that the barrier property can be sufficiently ensured. In addition, the aluminum oxide film 50 includes a film-like portion 51 and particles 53. According to this structure, compared with the case where the aluminum oxide film 50 is entirely composed of the film-like portion 51, the stress of the aluminum oxide film 50 can be released between the particles 53. Therefore, it is possible to prevent the stress in the aluminum oxide film 50 from being locally increased, and thus the generation of cracks can be suppressed even when an external force acts. In addition, since the interval P between the particles 53 is less than 1.3 μm, when an impact is applied from the outside of the particle 53 layer, etc., it is possible to prevent the impact from being concentrated on one particle 53. That is, as long as the interval P between the particles 53 is as described above, the substrate 20 can be protected.

[0075] (2) In the above embodiment, the ratio of the average value of the thickness of the particle layer 52 to the average value of the thickness of the aluminum oxide film 50 is 20% or more. According to this structure, the stress relaxation effect of the aluminum oxide film 50 by the particle layer 52 can be fully obtained. In addition, in the above embodiment, the ratio of the average value of the thickness of the particle layer 52 to the average value of the thickness of the aluminum oxide film 50 is 70% or less. According to this structure, the barrier property using the film-like portion 51 can be fully obtained.

[0076] (3) In the above embodiment, the arithmetic mean roughness of the outer surface 21 of the substrate 20 is 0.5 μm or less. Assuming that the arithmetic mean roughness of the outer surface 21 of the substrate 20 is relatively large, the outer surface of the film-like portion 51 may also reflect the unevenness of the outer surface 21 of the substrate 20. In this way, when the outer surface of the film-like portion 51 has unevenness, the particles 53 are retained in the depressions of the film-like portion 51 during manufacturing, and it is difficult for the particles 53 to be evenly located on the outer surface of the film-like portion 51. According to the above structure, since the arithmetic mean roughness of the outer surface 21 of the substrate 20 is relatively small, it is possible to suppress the particles 53 from being unevenly located on the outer surface of the film-like portion 51 as described above.

[0077] (4) According to the above embodiment, the composition ratio of atoms contained in the raw material is constant in the atomization step S14, the supply step S15, the first heating step S16, and the second heating step S17. According to this structure, the composition ratio does not change in the step of forming the film-like portion 51 or in the step of forming the particles 53. The composition ratios in the film-like portion 51 and the particles 53 are substantially the same, so that a boundary is not easily generated between these components, and the particles 53 are not easily detached from the film-like portion 51.

[0078] <Change Example>

[0079] The above-described embodiment and the following modified examples can be implemented in combination with each other within the scope of no technical contradiction.

[0080] In the above embodiment, the electronic component 10 is not limited to a negative characteristic thermistor component. For example, the electronic component 10 may be a piezoelectric component, a multilayer ceramic capacitor, an inductor, or the like.

[0081] In the above embodiment, the number of the first internal electrodes 41 and the second internal electrodes 42 is not limited to the example in the above embodiment. The number of the first internal electrodes 41 may be less than two or more than two. The same applies to the second internal electrodes 42 in this regard.

[0082] In the above embodiment, the material of the first underlying electrode 61A and the material of the second underlying electrode 62A are not limited to the examples in the above embodiment. For example, the material of the first underlying electrode 61A and the material of the second underlying electrode 62A may be a mixture of silver and glass.

[0083] In the above embodiment, the aluminum oxide film 50 does not have to cover the entire substrate 20 . The aluminum oxide film 50 may be configured to cover at least a portion of the outer surface 21 of the substrate 20 .

[0084] In the above embodiment, the interval P between the particles 53 in the aluminum oxide film 50 is not limited to the example of the above embodiment as long as it is 1.3 μm or less.

[0085] In the above embodiment, the average value of the thickness of the aluminum oxide film 50 is not limited to the example of the above embodiment as long as it is 0.05 μm or more and 2.0 μm or less.

[0086] In the above embodiment, the ratio of the average value of the thickness of the particle layer 52 to the average value of the thickness of the aluminum oxide film 50 may be less than 20%, or may be greater than 70%. The greater the ratio of the particle layer 52 in the aluminum oxide film 50, the more stress in the aluminum oxide film 50 can be expected to be suppressed. In addition, the greater the ratio of the film-like portion 51 in the aluminum oxide film 50, the more the barrier property of the aluminum oxide film 50 can be expected to be improved.

[0087] In the above embodiment, the aluminum oxide film 50 may contain other atoms in addition to oxygen atoms and aluminum atoms. For example, the aluminum oxide film 50 may contain other atoms in addition to carbon atoms and hydrogen atoms. In addition, the aluminum oxide film 50 may not contain carbon atoms and hydrogen atoms.

[0088] In the above embodiment, the chemical substances of the raw materials used in the atomizing step S14, the supplying step S15, the first heating step S16, and the second heating step S17 are not limited to the examples in the above embodiment. For example, the raw materials may also be organic salts and organic solvents containing aluminum. In addition, the raw materials may contain water or may not contain water.

[0089] In the above embodiment, the composition ratio of atoms contained in the raw material may be changed during the execution of the atomizing step S14, the supplying step S15, the first heating step S16, and the second heating step S17. Even when the composition ratio of the raw material is changed, the aluminum oxide film 50 may be configured such that the total atomic percentage of aluminum atoms and oxygen atoms is 80% or more, and the main component is aluminum oxide.

[0090] In the above embodiment, the arithmetic mean roughness of the outer surface 21 of the substrate 20 is not limited to the example of the above embodiment. For example, the arithmetic mean roughness of the outer surface 21 of the substrate 20 may be larger than 0.5 μm.

[0091] In the above embodiment, the film-like portion 51 and the particle layer 52 are formed by the difference in heating temperature between the first heating step S16 and the second heating step S17, but the film-like portion 51 and the particle layer 52 may be formed by other methods. For example, the film-like portion 51 and the particle layer 52 may be formed by making the frequency of the ultrasonic wave in the ultrasonic wave generating device 92A different. In addition, in the above embodiment, the film forming method of the aluminum oxide film 50 is not limited to the method of attaching the mist-like raw material to the substrate 20.

[0092] <Note>

[0093] The following describes technical ideas derived from the above-mentioned embodiments and modified examples.

[0094] [1] An electronic component comprising a substrate and an aluminum oxide film covering the outer surface of the substrate, the aluminum oxide film having an aluminum oxide film portion in contact with the outer surface of the substrate, and a particle layer located on the outer surface side of the film portion, the particle layer comprising a plurality of aluminum oxide particles bonded to the outer surface of the film portion, the aluminum oxide film including the film portion and the particle layer having an average thickness of not less than 0.05 μm and not more than 2.0 μm, and the spacing between the particles is not more than 1.3 μm.

[0095] [2] The electronic component according to [1], wherein a ratio of an average value of the thickness of the particle layer to an average value of the thickness of the aluminum oxide film is 20% or more and 70% or less.

[0096] [3] The electronic component according to [1] or [2], wherein the arithmetic mean roughness of the outer surface of the substrate is 0.5 μm or less.

[0097] [4] A film forming method is a film forming method for forming an aluminum oxide film on the outer surface of a substrate, comprising: a loading step of loading the substrate into a first chamber capable of heating the internal environment; an atomization step of forming a liquid raw material containing aluminum atoms and oxygen atoms into a mist in a second chamber using ultrasonic waves; a supply step of supplying the atomized raw material together with a carrier gas from the second chamber to the first chamber; and a first heating step of heating the first chamber to a first temperature while performing the supply step, and a second heating step of heating the first chamber to a second temperature that is specified to be lower than the first temperature while performing the supply step after the first heating step.

[0098] [5] According to the film forming method described in [4], during the execution of the above-mentioned atomization step, the above-mentioned supply step, the above-mentioned first heating step and the above-mentioned second heating step, the composition ratio of atoms contained in the above-mentioned raw material is kept constant.

[0099] Description of Reference Numerals

[0100] 10…electronic component; 20…substrate; 21…external surface; 41…first internal electrode; 42…second internal electrode; 50…aluminum oxide film; 51…membrane portion; 52…particle layer; 53…particles; 61…first external electrode; 62…second external electrode.

Claims

1. An electronic component, wherein: have: matrix; and an aluminum oxide film covering the outer surface of the substrate, The aluminum oxide film includes an aluminum oxide film portion in contact with the outer surface of the substrate, and a particle layer located on the outer surface side of the film portion. The particle layer includes a plurality of particles made of aluminum oxide bonded to the outer surface of the membrane portion. The average value of the thickness of the aluminum oxide film including the film-like portion and the particle layer is 0.05 μm or more and 2.0 μm or less, The distance between the particles is 1.3 μm or less.

2. The electronic component according to claim 1, wherein A ratio of an average value of the thickness of the particle layer to an average value of the thickness of the aluminum oxide film is 20% or more and 70% or less.

3. The electronic component according to claim 1 or 2, wherein: The arithmetic mean roughness of the outer surface of the substrate is 0.5 μm or less.

4. A film forming method, which is a film forming method for forming an aluminum oxide film on the outer surface of a substrate, wherein: have: A step of placing the substrate into a first chamber capable of heating the internal environment; In the atomization step, in the second chamber, ultrasonic waves are used to form the liquid raw material containing aluminum atoms and oxygen atoms into a mist; a supplying step of supplying the atomized raw material together with a carrier gas from the second chamber into the first chamber; and a first heating step of heating the first chamber to a first temperature while performing the supplying step; The method further includes a second heating step of heating the first chamber to a second temperature while performing the supply step after the first heating step, wherein the second temperature is set to be lower than the first temperature.

5. The film forming method according to claim 4, wherein: During the execution of the atomizing step, the supplying step, the first heating step, and the second heating step, the composition ratio of atoms contained in the raw material is kept constant.

Images