Multilayer ceramic capacitor

Abstract

The utility model belongs to the technical field of capacitors, and particularly relates to a multilayer ceramic capacitor. The multilayer ceramic capacitor comprises a first external electrode, a ceramic chip and a second external electrode which are connected in sequence. The ceramic chip comprises a laminated body and a shell; the laminated body comprises dielectric material layers, first internal electrodes and second internal electrodes which are alternately laminated, and has a first main surface and a second main surface which are opposite to each other in a thickness direction, a first side surface and a second side surface which are opposite to each other in a width direction, and a first end surface and a second end surface which are opposite to each other in a length direction; the first external electrode is connected to the first internal electrode, and the second external electrode is connected to the second internal electrode. The multilayer ceramic capacitor provided by the utility model is not easy to crack and strip between layers, has good electrical performance and moisture-proof reliability, and is low in noise.

Description

Technical Field

[0001] The utility model belongs to the technical field of ceramic capacitors, and in particular relates to a multilayer ceramic capacitor. Background Art

[0002] Multilayer ceramic capacitors (MLCCs) typically consist of two or more external electrodes, multiple internal electrodes, and multiple layers of dielectric material. Within the capacitor, layers of metal internal electrodes and dielectric material are stacked alternately. MLCCs, with their compact structure, high capacitance, and ease of installation, are widely used in electronic products such as imaging devices (LCDs and plasma display panels), computers, personal digital assistants (PDAs), and mobile phones.

[0003] In recent years, in order to achieve the small size and high capacity of MLCC and maximize the effective area of ​​the electrode, a method has been adopted in the manufacture of MLCC to maximize the area of ​​the internal electrode in the width direction by adopting a borderless design, and then separately attaching the side edges to both sides of the width direction of the capacitor green body and sintering. However, in this method, the bond between the side edges and the ceramic body is not necessarily strong, and gaps are prone to appear. In addition, the layers between the layers of the laminate are prone to cracking and peeling, resulting in reduced moisture resistance reliability of the MLCC product. In addition, some dielectric materials of MLCC have an inverse piezoelectric effect. When a changing electric field is applied to the MLCC, electrostriction occurs. At this time, the vibration generated on the MLCC is transmitted to the circuit board through the solder, causing the circuit board to vibrate, resulting in "howling" and generating noise.

[0004] Therefore, it is very important to provide a multilayer ceramic capacitor that is not prone to interlayer cracking and delamination, has good moisture resistance and reliability, and has low noise. Utility Model Content

[0005] The present invention aims to solve one or more technical problems existing in the above-mentioned prior art. Specifically, the present invention provides a multilayer ceramic capacitor with a more rational structural design, less prone to cracking and peeling between the layers of the laminate, good moisture resistance and reliability, and low noise.

[0006] Specifically, the multilayer ceramic capacitor includes a first external electrode, a ceramic chip, and a second external electrode connected in sequence;

[0007] The ceramic chip includes a laminate and a shell;

[0008] The laminate includes alternately stacked dielectric material layers, first and second internal electrodes, and has first and second main surfaces opposite to each other in a thickness direction, first and second side surfaces opposite to each other in a width direction, and first and second end surfaces opposite to each other in a length direction;

[0009] The shell covers the first main surface, the second main surface, the first side surface and the second side surface of the stack;

[0010] The first outer electrode is connected to the first inner electrode, and the second outer electrode is connected to the second inner electrode.

[0011] Specifically, each group of adjacent first internal electrodes and second internal electrodes is separated by the dielectric material layer, and the uppermost layer and the lowermost layer of the stack are both dielectric material layers.

[0012] Preferably, the shell includes a thickened portion and a non-thickened portion, and the thickened portion is the shell corresponding to the first main surface, the second main surface, the first side surface or the second side surface.

[0013] Preferably, the non-thickened portion is the shell corresponding to a surface other than the surface where the thickened portion is located.

[0014] Specifically, if the shell corresponding to the first main surface is a thickened portion, then the shell corresponding to the second main surface, the first side surface, and the second side surface is a non-thickened portion.

[0015] Preferably, the ratio of the thickness of the thickened portion to the thickness of the non-thickened portion is (1-2.5):1; further preferably, the ratio of the thickness of the thickened portion to the thickness of the non-thickened portion is (1.5-2):1.

[0016] Preferably, the housing corresponding to the first main surface, the second main surface, the first side surface or the second side surface of the multilayer ceramic capacitor has a protruding rib.

[0017] Preferably, the ratio of the thickness of the protruding rib to the thickness of the shell is (1-2.5):1; further preferably, the ratio of the thickness of the protruding rib to the thickness of the shell is (1.5-2):1.

[0018] Specifically, when the thickness ratio is greater than 2.5, it is difficult to ensure the strength of the protruding ribs, or the capacitor may become too large.

[0019] Preferably, the ratio of the area of ​​the surface where the protruding ribs are located covered by the protruding ribs to the total area of ​​the surface where the protruding ribs are located is (0.18-1):1; further preferably, the ratio of the area of ​​the surface where the protruding ribs are located covered by the protruding ribs to the total area of ​​the surface where the protruding ribs are located is (0.2-1):1.

[0020] Preferably, the protruding rib extends from a boundary between the surface where the protruding rib is located and the first end surface to a boundary between the surface where the protruding rib is located and the second end surface.

[0021] Preferably, in a cross section parallel to the first end surface, the cross-sectional shape of the protruding rib is any one of a triangle, a quadrilateral, and a semicircle.

[0022] Preferably, the quadrilateral includes any one of a quadrilateral, a trapezoid, a rectangle, and a parallelogram.

[0023] Preferably, the multilayer ceramic capacitor is mounted on a circuit board, and the surface where the thickened portion or the protruding rib is located is attached to the circuit board.

[0024] Specifically, some dielectric materials in MLCCs exhibit the inverse piezoelectric effect. When a varying electric field is applied to the MLCC, electrostriction occurs. The vibrations generated in the MLCC are transmitted through the solder to the circuit board, causing vibrations in the circuit board and resulting in "squealing." By increasing the thickness of the housing or adding protruding ribs on the surface where the MLCC is attached to the circuit board, the distance between the dielectric material layer and the circuit board is increased, absorbing some of the vibrations and alleviating the "squealing" problem, thereby reducing noise.

[0025] Preferably, the shell has a thickness of 10-50 μm.

[0026] Preferably, the dielectric material includes barium titanate; the material of the first inner electrode and the second inner electrode includes nickel; and the material of the first outer electrode and the second outer electrode includes copper.

[0027] Preferably, the material of the shell includes at least one of barium titanate and zirconium oxide.

[0028] Specifically, the shell material can be the same as the dielectric material, or a different ceramic material. The shell material can be a Class I dielectric with a smaller inverse piezoelectric effect to further reduce noise. Materials such as zirconia can also be used to further increase strength and reliability. When selecting the shell material, ensure that its thermal expansion coefficient is close to that of the ceramic chip material to prevent detachment and peeling.

[0029] Preferably, the method for preparing the multilayer ceramic capacitor comprises the following steps:

[0030] (1) preparing a ceramic slurry, forming a ceramic green sheet by a tape casting method, and printing a conductive pattern on the ceramic green sheet;

[0031] (2) stacking and pressing the ceramic green sheets with the conductive patterns into a laminated ceramic green sheet;

[0032] (3) cutting along a direction parallel to the first side surface or the second side surface to divide the laminated ceramic green sheet into a plurality of laminated green strips; extruding the laminated green strips together with the shell raw material by an extrusion molding method, and then cutting the laminated green strips along a direction parallel to the first end surface to form ceramic chip green strips;

[0033] (4) Sintering the ceramic chip green body to obtain a ceramic chip;

[0034] (5) External electrodes are formed on the first end surface and the second end surface of the laminated body to obtain a multilayer ceramic capacitor.

[0035] Specifically, after the ceramic green sheet with the printed conductive pattern in step (1) is sintered, the organic matter in the ceramic green sheet is pyrolyzed, and the ceramic particles are compacted to form a dielectric material; similarly, after sintering, the organic matter in the conductive pattern is pyrolyzed, and a conductive path is formed between the metals, forming the first internal electrode and the second internal electrode.

[0036] Preferably, in step (3), the extrusion molding includes the following steps: placing the laminate green strip into an extrusion molding device, the extrusion molding device having a guide structure to ensure that the laminate green strip is pushed out from the middle of the nozzle; adding the shell raw material to the extrusion molding device, the shell raw material is extruded in a shape covering the outer periphery of the laminate green strip under the extrusion of the extrusion molding device; starting the extrusion molding device, the extrusion molding device presses the laminate green strip and the shell raw material out of the nozzle together, thereby forming a laminate green strip covered with the shell green strip.

[0037] Specifically, the shell in the present invention is obtained by extrusion molding after cutting the stacked ceramic green sheets. Therefore, when designing the printed pattern, the position of the internal electrode pattern can be more compact, so that the effective area of ​​the electrode is maximized; the more compact internal electrode pattern design can alleviate the problem of reduced capacitance due to the reduction in the facing area of ​​the first internal electrode and the second internal electrode caused by inaccurate stacking alignment.

[0038] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0039] (1) The utility model can ensure that the MLCC product has good electrical performance and moisture resistance reliability through the integrated shell structure; it can constrain the dielectric layers and internal electrodes of each layer of the stack in the thickness direction to prevent interlayer cracking and peeling of each layer of the stack.

[0040] (2) The present invention extends the distance between the dielectric material layer and the circuit board by thickening the shell or adding a protruding rib structure on the surface of the circuit board, absorbs part of the vibration, alleviates the "howling" problem, and thus reduces noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic structural diagram of a multilayer ceramic capacitor in an assembled state according to Example 1 of the present utility model;

[0042] Figure 2 This is a schematic structural diagram of a multilayer ceramic capacitor in a disassembled state according to Example 1 of the present utility model;

[0043] Figure 3 This is a schematic structural diagram of a laminate according to Example 1 of the present utility model;

[0044] Figure 4 This is an exploded schematic diagram of the stacked structure of Example 1 of the present utility model;

[0045] Figure 5 This is a bottom view of a multilayer ceramic capacitor according to Example 1 of the present utility model;

[0046] Figure 6 This is a bottom view of the ceramic chip of Example 1 of the present utility model;

[0047] Figure 7 This is a schematic cross-sectional view of a ceramic chip perpendicular to its length in Example 1 of the present utility model;

[0048] Figure 8 This is a schematic cross-sectional view of a ceramic chip according to Example 2 of the present invention perpendicular to its length direction;

[0049] Figure 9 This is a schematic cross-sectional view of a ceramic chip perpendicular to its length direction in Example 3 of the present utility model;

[0050] Figure 10 This is a schematic cross-sectional view of a ceramic chip according to Example 4 of the present invention, perpendicular to its length direction;

[0051] Figure 11 This is a schematic cross-sectional view of a ceramic chip according to Example 7 of the present invention, perpendicular to its length direction;

[0052] Figure 12 This is a schematic cross-sectional view of a ceramic chip perpendicular to its length in Example 8 of the present utility model;

[0053] Figure 13 This is a schematic structural diagram of a multilayer ceramic capacitor according to comparative example 1 of the present invention.

[0054] In Example 1, 1 is a ceramic chip, 2 is a first external electrode, 3 is a second external electrode, 4 is a laminate, 5 is a housing, 6 is a dielectric material layer, 7 is a first internal electrode, 8 is a second internal electrode, 9 is a first main surface, 10 is a second main surface, 11 is a first side surface, 12 is a second side surface, 13 is a first end surface, 14 is a second end surface, and 15 is a protruding rib;

[0055] In Comparative Example 1, 2' is the first outer electrode, 3' is the second outer electrode, 4' is the laminate, 6' is the dielectric material layer, 7' is the first inner electrode, 8' is the second inner electrode, 16 is the upper cover sheet, 17 is the lower cover sheet, 18 is the first side edge portion, and 19 is the second side edge portion. DETAILED DESCRIPTION

[0056] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0057] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0058] In the embodiments of the present invention, the dielectric material and the shell material are uniformly barium titanate, the inner electrode material is uniformly nickel electrode, and the outer electrode is uniformly copper electrode.

[0059] Example 1

[0060] like Figure 1-4 As shown, the multilayer ceramic capacitor of Example 1 includes a ceramic chip 1, a first external electrode 2 and a second external electrode 3 located at both ends of the ceramic chip 1; the ceramic chip 1 includes a laminate 4 and a shell 5, the laminate 4 includes alternately stacked dielectric material layers 6, first internal electrodes 7 and second internal electrodes 8 (each group of adjacent first internal electrodes 7 and second internal electrodes 8 is separated by a dielectric material layer 6, and the uppermost layer and the lowermost layer of the laminate 4 are both dielectric material layers 6), and has a first main surface 9 and a second main surface 10 opposite to each other in the thickness direction, a first side surface 11 and a second side surface 12 opposite to each other in the width direction, and a first end surface 13 and a second end surface 14 opposite to each other in the length direction;

[0061] The shell 5 covers the first main surface 9, the second main surface 10, the first side surface 11 and the second side surface 12 of the laminate 4. The thickness of the shell 5 is 20 μm.

[0062] The first external electrode 2 and the second external electrode 3 are respectively provided on the first end surface 13 and the second end surface 14 of the stacked body 4. The first external electrode 2 is electrically connected to the first internal electrode 7, and the second external electrode 3 is electrically connected to the second internal electrode 8.

[0063] The second main surface 10 of the laminate 4 is attached to a circuit board, and the housing 5 has two protruding ribs 15 on the second main surface 10 .

[0064] like Figure 5-6 As shown, the ratio of the area S1 covered by the protruding rib 15 on the second major surface 10 to the total area S of the second major surface 10 is 0.4.

[0065] like Figure 7 As shown, the ratio of the thickness H2 of the protruding rib 15 in the stacking direction of the stacked body 4 (perpendicular to the second main surface) to the thickness H (20 μm) of the shell 5 is H2:H=1.5, and the cross-sectional shape of the protruding rib 15 is a curved quadrilateral.

[0066] Example 2

[0067] The multilayer ceramic capacitor provided in Example 2 differs from that in Example 1 only in that the shell 5 of Example 2 does not have protruding ribs, and the thickness of the shell 5 corresponding to the first main surface 9, the second main surface 10, the first side surface 11 and the second side surface 12 of the stack 4 is 10 μm, and the rest is the same as in Example 1.

[0068] Example 2 The cross-sectional view of the ceramic chip 1 perpendicular to the length direction is shown in FIG. Figure 8 shown.

[0069] Example 3

[0070] The multilayer ceramic capacitor provided in Example 3 is different from that in Example 1 only in that: in Example 3, the surface to which the circuit board is attached is the first side surface 11 of the laminate 4, the shell 5 has two protruding ribs 15 on the first side surface 11, the ratio of the thickness H2 of the protruding rib 15 in the width direction of the multilayer ceramic capacitor to the thickness H (20 μm) of the shell 5 is H2:H=2, the ratio of the area covered by the protruding rib 15 on the first side surface 11 to the total area of ​​the first side surface 11 is 0.5, the cross-sectional shape of the protruding rib 15 is a curved quadrilateral, and the rest is the same as in Example 1.

[0071] Example 3 The cross-sectional view of the ceramic chip 1 perpendicular to the length direction is shown in FIG. Figure 9 shown.

[0072] Example 4

[0073] The multilayer ceramic capacitor provided in Example 4 differs from that in Example 1 only in that the shell 5 of Example 4 does not have protruding ribs, but the shell corresponding to the second main surface 10 of the laminate 4 is a thickened portion, the thickness H1 of which is greater than the thickness H (20 μm) of the shell 5 on other surfaces, and the thickness ratio H1:H=2.5. The rest is the same as Example 1.

[0074] Example 4 The cross-sectional view of the ceramic chip 1 perpendicular to the length direction is shown in FIG. Figure 10 shown.

[0075] Example 5

[0076] The multilayer ceramic capacitor structure provided in Example 5 differs from that in Example 1 only in that the ratio of the area S1 covered by the protruding rib 15 on the second main surface 10 to the total area S of the second main surface 10 is 0.2, and the ratio of the thickness H2 of the protruding rib 15 in the stacking direction of the multilayer ceramic capacitor to the thickness H of the shell 5 is H2:H=2.5. The rest is the same as in Example 1.

[0077] Example 6

[0078] The multilayer ceramic capacitor structure provided in Example 6 differs from that in Example 2 only in that the thickness of the shell 5 corresponding to the first main surface 9 , the second main surface 10 , the first side surface 11 and the second side surface 12 is 50 μm, and the rest is the same as in Example 2.

[0079] Example 7

[0080] The multilayer ceramic capacitor structure provided in Example 7 differs from that in Example 1 only in that: the ratio of the area S1 covered by the protruding rib 15 on the second main surface 10 to the total area S of the second main surface 10 is 0.8, the ratio of the thickness H2 of the protruding rib 15 in the capacitor stacking direction to the thickness H of the shell 5 is H2:H=2.5, the cross-sectional shape of the protruding rib 15 is trapezoidal, and the rest is the same as in Example 1.

[0081] Example 7 The cross-sectional view of the ceramic chip 1 perpendicular to the length direction is shown in FIG. Figure 11 shown.

[0082] Example 8

[0083] The multilayer ceramic capacitor structure provided in Example 8 differs from that in Example 1 only in that the ratio of the area S1 covered by the protruding rib 15 on the second main surface 10 to the total area S of the second main surface 10 is 0.6, the thickness of the shell 5 is 30 μm, and the cross-sectional shape of the protruding rib 15 is semicircular. The rest is the same as in Example 1.

[0084] The cross-sectional view of the ceramic chip 1 in the embodiment 8 perpendicular to the length direction is shown in FIG. Figure 12 shown.

[0085] The structural parameters of the multilayer ceramic capacitors of Examples 1-8 are shown in Table 1.

[0086] Table 1: Structural parameters of multilayer ceramic capacitors in Examples 1-8

[0087]

[0088]

[0089] Comparative Example 1

[0090] Comparative Example 1 adopts the common edgeless design in the prior art. The structural diagram of the multilayer ceramic capacitor of Comparative Example 1 is shown as follows: Figure 13 As shown. Figure 13 The multilayer ceramic capacitor includes a ceramic chip and external electrodes, the external electrodes include a first external electrode 2' and a second external electrode 3', the ceramic chip includes a laminate 4', a side edge portion and a cover sheet, the laminate 4' includes alternately stacked dielectric material layers 6', a first internal electrode 7' and a second internal electrode 8', and has a first main surface and a second main surface opposite to each other in the thickness direction, a first side surface and a second side surface opposite to each other in the width direction, and a first end surface and a second end surface opposite to each other in the length direction;

[0091] The cover sheet includes an upper cover sheet 16 disposed on the first main surface of the stack 4 ′ and a lower cover sheet 17 disposed on the second main surface of the stack 4 ′;

[0092] The side edge portion includes a first side edge portion 18 provided on a first side surface of the stacked body 4 ′ and a second side edge portion 19 provided on a second side surface of the stacked body 4 ′;

[0093] The first external electrode 2' and the second external electrode 3' are respectively arranged on the first end surface and the second end surface of the stack 4'. The first external electrode 2' is electrically connected to the first internal electrode 7', and the second external electrode 3' is electrically connected to the second internal electrode 8'.

[0094] Performance Testing

[0095] The multilayer ceramic capacitors prepared in Examples 1-8 and the multilayer ceramic capacitor of Comparative Example 1 were subjected to moisture resistance and noise tests. The specific test methods are as follows:

[0096] Moisture resistance test: One batch of samples was made for each of Examples 1-8 and Comparative Example 1, that is, 1,000 multilayer ceramic capacitor samples were made for each batch. The electrical properties (insulation performance and capacitance) of each batch of samples were tested after 24 hours of treatment at a temperature of 85°C, a relative humidity of 85%, and a voltage of 12.6V, and the proportion of failed samples was counted.

[0097] Noise test: One batch of samples was prepared for each of Examples 1-8 and Comparative Example 1, i.e., 1,000 multilayer ceramic capacitor samples were prepared for each batch. The samples were soldered to a circuit board, and the circuit board was placed in a silent box. A power resistor was used as a load, and an AC voltage with a frequency of 20-20,000 Hz and a voltage of 10 kV / mm was applied to the sample. The maximum sound pressure level of the sound was then measured and recorded using a noise meter.

[0098] The moisture resistance and noise test results of the multilayer ceramic capacitors of Examples 1-8 and Comparative Example 1 are shown in Table 2.

[0099] Table 2: Moisture resistance and noise test results of multilayer ceramic capacitors of Examples 1-8 and Comparative Example 1

[0100] Group Moisture resistance defective rate / % Noise / dB Example 1 0.3 32 Example 2 0.5 41 Example 3 0.4 28 Example 4 0.5 35 Example 5 0.3 26 Example 6 0.3 40 Example 7 0.5 29 Example 8 0.4 27 Comparative Example 1 1.9 46

[0101] As can be seen from Table 2, the multilayer ceramic capacitor of the present invention has good moisture resistance and low noise.

[0102] By comparing Examples 2, 4, and 6 with Examples 1, 3, 5, and 7-8, it can be seen that the noise of the capacitor can be reduced by thickening the shell structure or adding a protruding rib structure on the surface of the attached circuit board.

[0103] Comparative Example 1 adopts a conventional structure in the prior art, so that the moisture resistance of Comparative Example 1 is significantly worse than that of the present application, and the noise is significantly greater than that of the present application.

[0104] In summary, the present invention, through its integrated housing structure, ensures that MLCC products possess excellent electrical performance and moisture-resistant reliability. It also constrains the dielectric layers and internal electrodes of the laminate in the thickness direction, preventing interlayer cracking and delamination. Furthermore, by increasing the housing thickness or adding protruding ribs on the surface of the printed circuit board, the distance between the dielectric material layer and the printed circuit board is extended, absorbing some vibrations and alleviating the "whistling" problem, thereby reducing noise.

[0105] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A multilayer ceramic capacitor, characterized in that comprising a first external electrode, a ceramic chip and a second external electrode connected in sequence; The ceramic chip includes a laminate and a shell; The laminate includes alternately stacked dielectric material layers, first and second internal electrodes, and has first and second main surfaces opposite to each other in a thickness direction, first and second side surfaces opposite to each other in a width direction, and first and second end surfaces opposite to each other in a length direction; The shell covers the first main surface, the second main surface, the first side surface and the second side surface of the stack; The first outer electrode is connected to the first inner electrode, and the second outer electrode is connected to the second inner electrode.

2. The multilayer ceramic capacitor according to claim 1, wherein The shell includes a thickened portion and a non-thickened portion, and the thickened portion is the shell corresponding to the first main surface, the second main surface, the first side surface or the second side surface.

3. The multilayer ceramic capacitor according to claim 2, wherein The ratio of the thickness of the thickened portion to the thickness of the non-thickened portion is (1-2.5):

1.

4. The multilayer ceramic capacitor according to claim 1, wherein The case corresponding to the first main surface, the second main surface, the first side surface, or the second side surface of the multilayer ceramic capacitor has a protruding rib.

5. The multilayer ceramic capacitor according to claim 4, wherein The protruding rib extends from a boundary between the surface where the protruding rib is located and the first end surface to a boundary between the surface where the protruding rib is located and the second end surface.

6. The multilayer ceramic capacitor according to claim 4, wherein The ratio of the thickness of the protruding rib to the thickness of the shell is (1-2.5):

1.

7. The multilayer ceramic capacitor according to claim 4, wherein The ratio of the area of ​​the surface where the protruding ribs are located covered by the protruding ribs to the total area of ​​the surface where the protruding ribs are located is (0.18-1):

1.

8. The multilayer ceramic capacitor according to claim 4, wherein In a cross section parallel to the first end surface, the cross section of the protruding rib is in any one of a triangle, a quadrilateral, and a semicircle.

9. The multilayer ceramic capacitor according to claim 8, wherein The quadrilateral includes any one of a quadrilateral, a trapezoid, a rectangle, and a parallelogram.

10. The multilayer ceramic capacitor according to claim 1, wherein The shell has a thickness of 10-50 μm.

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