Electronic components, and their mounting method and mounting structure

Abstract

Provided are an electronic component with an external electrode having sufficient thermal resistance, and a mounting method and a mounting structure therefor.　An electronic component 1 comprises: an element body 10 in which internal electrodes 16a, 16b are embedded and that has a first major surface 12a and a second major surface 12b opposing each other in a thickness direction T, a first side surface 13a and a second side surface 13b opposing each other in a width direction W orthogonal to the thickness direction T, and a first end surface 14a and a second end surface 14b opposing each other in a length direction L orthogonal to both the thickness direction T and the width direction W; and a pair of external electrodes 20a, 20b disposed on at least the first end surface 14a and the second end surface 14b of the element body 10 and connected to the internal electrodes 16a, 16b. The external electrodes 20a, 20b each comprise at least an Ni plating layer 21, and a Cu6Sn5 portion 23 disposed on the Ni plating layer 21 either directly or indirectly with an island-like or layer-like Cu-based interposed portion 22 therebetween.

Description

[Technical Field]

[0001] The present invention relates to an electronic component, and a mounting method and structure thereof. [Background technology]

[0002] As electronic devices such as mobile phones become smaller and CPU speeds increase, demand for multilayer ceramic capacitors (MLCCs) is increasing.

[0003] Here, for example, Patent Document 1 describes an example of a multilayer ceramic capacitor, which includes a ceramic body including a dielectric layer and first and second internal electrodes stacked so as to be alternately exposed on first and second outer sides with the dielectric layer sandwiched therebetween, and first and second external electrodes arranged on the first and second outer sides of the ceramic body so as to be connected to corresponding ones of the first and second internal electrodes, wherein the first and second external electrodes include first and second base electrode layers at least partially in contact with the first and second outer sides of the ceramic body, first and second nickel plating layers arranged so as to cover the first and second base electrode layers, respectively, and first and second tin plating layers arranged so as to cover the first and second nickel plating layers, respectively, and wherein the thickness of the center portion of each of the first and second tin plating layers exceeds 5 μm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-61537 Summary of the Invention [Problem to be solved by the invention]

[0005] In multilayer ceramic electronic components in which the (first and second) base electrode layers of the external electrodes contain copper, the copper in the base electrode layers is likely to diffuse into the tin plating layer, causing copper to disappear from the base electrode layer when bonding to the land on the circuit board, which could lead to mounting defects. In this regard, the multilayer ceramic electronic component in Patent Document 1 has a nickel plating layer that covers the base electrode layer, making it difficult for copper to diffuse from the base electrode layer.

[0006] However, even if a nickel plating layer is provided to cover the base electrode layer, if the joining temperature becomes high during the reflow process in which the solder placed on the circuit board is heated to join the electronic component to the circuit board, or if the component is exposed to a high-temperature environment for a long period of time, nickel atoms contained in the nickel plating layer may diffuse into the solder, resulting in mounting defects. Therefore, the multilayer ceramic electronic component described in Patent Document 1 still leaves room for improvement in the heat resistance of the external electrodes.

[0007] Therefore, an object of the present invention is to provide an electronic component having an external electrode that has excellent heat resistance and effectively suppresses the generation of whiskers due to thermal shock, as well as a mounting method and mounting structure for the same. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided an electronic component comprising: an element body in which internal electrodes are embedded, the element body having first and second main surfaces opposing each other in a thickness direction, first and second side surfaces opposing each other in a width direction perpendicular to the thickness direction, and first and second end faces opposing each other in a length direction perpendicular to both the thickness direction and the width direction; and a pair of external electrodes disposed at least on the first and second end faces of the element body and connected to the internal electrodes, wherein the external electrodes have at least a Ni plating layer and a Cu6Sn5 portion disposed on the Ni plating layer directly or indirectly via an island-shaped or layer-shaped Cu-based intermediate portion. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an electronic component having an external electrode that has excellent heat resistance and effectively suppresses the generation of whiskers due to thermal shock, as well as a mounting method and mounting structure for the same. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an external perspective view showing an example of a multilayer ceramic capacitor, which is an electronic component. [Figure 2] 2 is a cross-sectional view taken along line II-II in FIG. 1, taken along a plane including the length direction L and the thickness direction T. FIG. [Figure 3] 3 is a cross-sectional view taken along the line III-III in FIG. 1 and cut along a plane including the width direction W and the thickness direction T. FIG. [Figure 4] Figure 4 shows partial cross-sectional views of various external electrodes formed with different layered structures, where Figure 4(a) is a partial cross-sectional view of an external electrode in which a Cu6Sn5 portion is arranged on a Ni plating layer via an island-shaped Cu-based intervening portion, Figure 4(b) is a partial cross-sectional view of an external electrode in which a Cu6Sn5 portion is arranged on a Ni plating layer via a layer-shaped Cu-based intervening portion, and Figure 4(c) is a partial cross-sectional view of an external electrode in which a Cu6Sn5 portion is arranged directly on a Ni plating layer. [Figure 5] Figure 5 is a partial cross-sectional view showing the layered structure of an external electrode when the Cu-based intermediate portion is a single intermediate portion, where Figure 5(a) is a partial cross-sectional view of an external electrode when an island-shaped Cu-based intermediate portion is arranged by a single intermediate portion formed by an island-shaped Cu3Sn portion, and Figure 5(b) is a partial cross-sectional view of an external electrode when a layered Cu-based intermediate portion is arranged by a single intermediate portion formed by a layered Cu3Sn portion. [Figure 6]Figure 6 is a partial cross-sectional view showing the layered structure of an external electrode when the Cu-based intermediate portion is a composite intermediate portion, where Figure 6(a) is a partial cross-sectional view of an external electrode when an island-shaped Cu-based intermediate portion is arranged by a composite intermediate portion formed of an island-shaped Cu portion and an island-shaped Cu3Sn portion, Figure 6(b) is a partial cross-sectional view of an external electrode when a layered Cu-based intermediate portion is arranged by a composite intermediate portion formed of an island-shaped Cu portion and a layered Cu3Sn portion, and Figure 6(c) is a partial cross-sectional view of an external electrode when a layered Cu-based intermediate portion is arranged by a composite intermediate portion formed of a layered Cu portion and a layered Cu3Sn portion. [Figure 7] 7A and 7B are schematic cross-sectional views showing a mounting method of an electronic component according to the present embodiment, in which FIG. 7A is a schematic cross-sectional view showing the state before reflowing an electronic component placed on a land of a circuit board via solder, and FIG. 7B is a schematic cross-sectional view showing the state when the electronic component is mounted on the circuit board after reflowing in the mounted state of FIG. 7A. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described with reference to the drawings. Note that the present invention is not limited to the following embodiment, and various modifications are possible within the scope of the present invention.

[0012] (1) Electronic Components Hereinafter, electronic components according to embodiments of the present invention will be described with reference to the drawings. In this embodiment, a multilayer ceramic capacitor will be used as an example of the electronic component. Note that in this embodiment, a typical two-terminal capacitor will be used as an example, but the present invention is not limited to this. In addition to multilayer ceramic capacitors, the present invention can also be applied to electrodes that connect to various external electronic components, such as multilayer LC filters having a coil and capacitance, multilayer ceramic inductors, multilayer ceramic thermistors, and even to multilayer components such as coils with wound conductors and modules in which electronic components are embedded in resin.

[0013] Fig. 1 is an external perspective view showing an example of a multilayer ceramic capacitor, which is an electronic component. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1, along a plane including a length direction L and a thickness direction T. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1, along a plane including a width direction W and a thickness direction T.

[0014] The electronic component 1 of this embodiment includes an element body 10 having internal electrodes 16a, 16b embedded therein, the element body 10 having first and second main surfaces 12a, 12b facing in a thickness direction T, first and second side surfaces 13a, 13b facing in a width direction W perpendicular to the thickness direction T, and first and second end surfaces 14a, 14b facing in a length direction L perpendicular to both the thickness direction T and the width direction W, and a pair of external electrodes 20a, 20b disposed on the first and second end surfaces 14a, 14b, respectively, of the element body 10 and connected to the internal electrodes 16a, 16b. Here, the external electrodes 20a, 20b at least have a Ni plating layer 21 and a Cu6Sn5 portion 23 disposed on the Ni plating layer 21 directly or indirectly via an island-shaped or layer-shaped Cu-based intermediate portion 22.

[0015] An example of a multilayer ceramic capacitor that is the electronic component 1 of this embodiment is one that has a rectangular parallelepiped element body 10 and two external electrodes 20a, 20b disposed on at least both end faces 14a, 14b of the element body 10, as shown in Fig. 1. The element body 10 may have any known configuration and is not limited to the rectangular parallelepiped shape shown in Fig. 1.

[0016] The element body 10 has a plurality of laminated ceramic layers 15 and a plurality of internal electrode layers 16a, 16b. The element body 10 further has a first main surface 12a and a second main surface 12b that face each other in a thickness direction T, a first side surface 13a and a second side surface 13b that face each other in a width direction W that is perpendicular to the thickness direction T, and a first end surface 14a and a second end surface 14b that face each other in a length direction L that is perpendicular to the thickness direction T and the width direction W. The dimensions of the element body 10 are not particularly limited. As shown in FIG. 1 , the dimension of the element body 10 along the length direction L is not necessarily longer than the dimension along the width direction W.

[0017] It is preferable that the corners and ridges of the rectangular parallelepiped of element body 10 are rounded. Here, the corners refer to the portions where three adjacent faces of element body 10 intersect, and the ridges refer to the portions where two adjacent faces of element body 10 intersect. Furthermore, unevenness may be formed on some or all of first main surface 12a and second main surface 12b, first side surface 13a and second side surface 13b, and first end surface 14a and second end surface 14b.

[0018] 2, the element body 10 has a structure in which the internal electrodes 16a, 16b are embedded in the ceramic layer 15. Here, the ceramic layer 15 in which the internal electrodes 16a, 16b are embedded includes an outer layer portion 15a and an inner layer portion 15b. Of these, the outer layer portion 15a is a portion of the ceramic layer that includes the first main surface 12a of the element body 10 and is located outside the internal electrode layer (internal electrode layer 16a in FIG. 2) closest to the first main surface 12a, and a portion of the ceramic layer that includes the second main surface 12b of the element body 10 and is located outside the internal electrode layer (internal electrode layer 16b in FIG. 2) closest to the second main surface 12b. The inner layer portion 15b is a portion of the ceramic layer that is partitioned by two adjacent internal electrode layers 16a, 16b facing each other. The thickness of the ceramic layer portion constituting the outer layer portion 15a is not particularly limited, but is preferably thicker than the ceramic layer portion constituting the inner layer portion 15b, and may be, for example, in the range of 20 μm to 300 μm.

[0019] The total number of ceramic layers (including inner layer portion 15b and two outer layer portions 15a) stacked in element body 10 is not particularly limited, but is preferably in the range of 15 to 2000.

[0020] The external dimensions of the element 10 are not particularly limited, but it is preferable that the dimension along the length direction L is in the range of 0.08 mm or more and 5.6 mm or less, the dimension along the width direction W is in the range of 0.04 mm or more and 4.9 mm or less, and the dimension along the thickness direction T is in the range of 0.04 mm or more and 2.9 mm or less.

[0021] When the electronic component 1 functions as a multilayer ceramic capacitor, the ceramic layers 15 included in the element body 10 are preferably made of a dielectric material. Examples of the dielectric material that can be used include dielectric ceramics containing a main component such as BaTiO3, CaTiO3, SrTiO3, or CaZrO3. When the dielectric material is a main component, it may contain a minor component, such as a manganese compound, an iron compound, a chromium compound, a cobalt compound, or a nickel compound, in a smaller amount than the main component, depending on the desired characteristics of the element body 10.

[0022] On the other hand, when electronic component 1 is to function as a thermistor element, ceramic layer 15 included in element body 10 is preferably made of a semiconducting ceramic. Here, for example, a spinel-based ceramic material can be used as the semiconducting ceramic material.

[0023] Furthermore, when electronic component 1 is to function as an inductor element, ceramic layer 15 included in element body 10 is preferably made of magnetic ceramic. Here, the magnetic ceramic material may be, for example, a ferrite ceramic material. In this case, the internal electrodes 16a, 16b of the element body 10 are preferably made of a conductor having a coiled shape.

[0024] The thickness of the ceramic layer 15 included in the element body 10 is not particularly limited, but is preferably in the range of 0.4 μm to 20 μm.

[0025] 1 to 3 has a plurality of first internal electrode layers 16a and a plurality of second internal electrode layers 16b, each having, for example, a substantially rectangular planar shape, embedded as the internal electrode layers 16. These first internal electrode layers 16a and second internal electrode layers 16b are preferably embedded so as to be alternately arranged at equal intervals with the ceramic layers 15 sandwiched between them along the thickness direction T of the element body 10.

[0026] 2, the first internal electrode layer 16a has a first opposing electrode portion 17a located opposite the second internal electrode layer 16b, and a first extraction electrode portion 18a located on the side of the first end face 14a of the element body 10 where one end of the first internal electrode layer 16a is located, and extending from the first opposing electrode portion 17a to the first end face 14a of the element body 10. An end of the first extraction electrode portion 18a is extracted to the first end face 14a and connected to a first external electrode 20a, which will be described later.

[0027] The second internal electrode layer 16b also has a second opposing electrode portion 17b located opposite the first internal electrode layer 16a, and a second extraction electrode portion 18b located on the second end face 14b side of the element body 10, where the other end of the second internal electrode layer 16b is located, and extending from the second opposing electrode portion 17b to the second end face 14b of the element body 10. The second extraction electrode portion 18b has an end portion that is extracted to the second end face 14b and is connected to a second external electrode 20b, which will be described later.

[0028] As shown in FIG. 2, the element body 10 is preferably configured such that the end of the first internal electrode layer 16a opposite the first extraction electrode portion 18a and the second end face 14b, and the end of the second internal electrode layer 16b opposite the second extraction electrode portion 18b and the first end face 14a are separated by ceramic layers 15 (these separated ceramic layer portions 19a, 19b are hereinafter referred to as "L gaps"). Furthermore, as shown in FIG. 3, it is preferable that the element body 10 is separated by ceramic layer 15 between one widthwise end of the first opposing electrode portion 17a and one widthwise end of the second opposing electrode portion 17b and the first side surface 13a, and between the other widthwise end of the first opposing electrode portion 17a and the other widthwise end of the second opposing electrode portion 17b and the second side surface 13b (these separated portions 19c, 19d are hereinafter referred to as "W gaps").

[0029] The internal electrode layers 16 can be made of an appropriate conductive material, such as a metal such as Ni, Cu, Ag, Pd, or Au, or an alloy containing at least one of these metals, such as an Ag-Pd alloy. The internal electrode layers 16 may further contain dielectric particles having the same composition as the ceramic contained in the ceramic layers 15.

[0030] The thickness of the internal electrode layer 16 is not particularly limited, but is preferably 0.3 μm or more and 2.0 μm or less. The total number of the internal electrode layers 16a, 16b is preferably approximately equal to the total number of the ceramic layers, more specifically, in the range of 15 to 2000.

[0031] 1 and 2, external electrodes are disposed on the first end face 14a and the second end face 14b of the element body 10. Here, the external electrodes are configured by a pair of external electrodes, a first external electrode 20a and a second external electrode 20b, which are electrically connected to the first internal electrode layer 16a and the second internal electrode layer 16b, respectively.

[0032] 1 shows the case where the first external electrode 20a is formed so as to extend from the first end face 14a so as to cover not only the first end face 14a but also a portion of each of the first and second main faces 12a and 12b and the first and second side faces 13a and 13b. In this case, the first external electrode 20a is electrically connected to the first lead electrode portion 18a of the first internal electrode layer 16a.

[0033] 1 shows the case where the second external electrode 20b is formed so as to extend from the second end face 14b so as to cover not only the second end face 14b but also a portion of each of the first and second main faces 12a and 12b and the first and second side faces 13a and 13b. In this case, the second external electrode 20b is electrically connected to the second extraction electrode portion 18b of the second internal electrode layer 16b.

[0034] In the element body 10, capacitance is formed by the first opposing electrode portion 17a of the first internal electrode layer 16a and the second opposing electrode portion 17b of the second internal electrode layer 16b facing each other via the ceramic layer 15. Therefore, capacitance can be obtained between the first external electrode 20a connected to the first internal electrode layer 16a and the second external electrode 20b connected to the second internal electrode layer 16b, and capacitor characteristics are exhibited.

[0035] The external electrode 20, i.e., one or both of the first external electrode 20a and the second external electrode 20b, has at least a Ni plating layer 21 and a Cu6Sn5 portion 23 disposed directly on the Ni plating layer 21 or indirectly via an island-shaped or layer-shaped Cu-based intermediate portion 22. Here, the Ni plating layer 21 is preferably disposed on the surface of the element body 10 with a base electrode layer 25 sandwiched therebetween. In addition, a Sn plating layer 24 is preferably disposed on the surface of the Cu6Sn5 portion 23.

[0036] 4(a), the electronic component of this embodiment can form the external electrode 20 by providing a Ni plating layer 21 on a base electrode layer 25, indirectly providing a Cu6Sn5 portion 23 on this Ni plating layer 21 via an island-shaped Cu-based intermediate portion 22, and providing a Sn plating layer 24 on the Cu6Sn5 portion 23. Alternatively, the electronic component of this embodiment can form the external electrode 20A by providing a Ni plating layer 21 on a base electrode layer 25, indirectly providing a Cu6Sn5 portion 23 on this Ni plating layer 21 via a layer-shaped Cu-based intermediate portion 22A, and providing a Sn plating layer 24 on the Cu6Sn5 portion 23, as shown in FIG. Furthermore, in the electronic component of this embodiment, as shown in FIG. 4(c), the external electrode 20B may be formed by disposing a Ni plating layer 21 on the base electrode layer 25, disposing a Cu6Sn5 portion 23 directly on this Ni plating layer 21, and disposing a Sn plating layer 24 on the Cu6Sn5 portion 23.

[0037] The base electrode layer 25 constituting the external electrode 20 is conductive and is arranged to cover the first end face 14a or the second end face 14b of the element body 10. Here, the base electrode layer 25 is preferably arranged on the first end face 14a or the second end face 14b of the element body 10 and extends from the first end face 14a or the second end face 14b to cover a portion of each of the first main face 12a and the second main face 12b and the first side face 13a and the second side face 13b.

[0038] The base electrode layer 25 may be made of a conductive metal or glass. Examples of the conductive metal contained in the base electrode layer 25 include metals such as Cu, Ni, Ag, Pb, and Au, and alloys such as Ag-Pb alloys. Examples of the glass contained in the base electrode layer 25 include glass containing one or more components selected from B, Si, Pd, Ba, Mg, Al, and Li. The base electrode layer 25 may be composed of multiple layers. The base electrode layer 25 may be formed by applying a conductive paste containing glass and a conductive metal to the element body 10 and baking it. More specifically, the base electrode layer 25 may be fired simultaneously with the ceramic layer 15 and the internal electrode layer 16, or may be fired after the ceramic layer 15 and the internal electrode layer 16 have been baked. The base electrode layer 25 preferably has a maximum thickness of 10 μm to 150 μm.

[0039] The Ni plating layer 21 is disposed on the end face of the element body 10 directly or with the base electrode layer 25 sandwiched therebetween. More preferably, the Ni plating layer 21 is disposed on the first end face 14a or the second end face 14b of the element body 10, and is disposed on the surface of the base electrode layer 25, which is provided so as to extend from the first end face 14a or the second end face 14b to the first main surface 12a and the second main surface 12b and the first side face 13a and the second side face 13b.

[0040] In this way, by providing the Ni plating layer 21 on the external electrode 20, it is possible to prevent the internal electrode layer 16 and the base electrode layer 25 from being eroded by the solder used in the reflow process when mounting the electronic component 1 on a circuit board.

[0041] The thickness of the Ni plating layer 21 is not particularly limited, but is preferably in the range of 1 μm or more and 15 μm or less.

[0042] The Cu-based intermediate portion 22 is optionally provided on the surface of the Ni plating layer 21. Here, the Cu-based intermediate portion 22 is preferably a single intermediate portion formed of island-shaped or layered Cu3Sn portions 26 on the Ni plating layer 21, or a composite intermediate portion formed by sequentially arranging a Cu portion 27 formed of island-shaped or layered Cu and a Cu3Sn portion 26 formed of island-shaped or layered Cu3Sn.

[0043] That is, the Cu-based intermediate portion may be a single intermediate portion formed of island-shaped Cu3Sn portions 26C formed on the Ni plating layer 21, such as the Cu-based intermediate portion 22C shown in Fig. 5(a). Alternatively, the Cu-based intermediate portion may be a single intermediate portion formed of layer-shaped Cu3Sn portions 26C formed on the Ni plating layer 21, such as the Cu-based intermediate portion 22D shown in Fig. 5(b).

[0044] The Cu-based intermediate portion may be a composite intermediate portion, such as a Cu-based intermediate portion 22E shown in Fig. 6(a), in which a Cu portion 27E formed of island-shaped Cu and a Cu3Sn portion 26E formed of island-shaped Cu3Sn are disposed in order on the Ni plating layer 21. The Cu-based intermediate portion may be a composite intermediate portion, such as a Cu-based intermediate portion 22F shown in Fig. 6(b), in which a Cu portion 27F formed of island-shaped Cu and a Cu3Sn portion 26F formed of layered Cu3Sn are disposed in order on the Ni plating layer 21. The Cu-based intermediate portion may be a composite intermediate portion, such as a Cu-based intermediate portion 22G shown in Fig. 6(c), in which a Cu portion 27G formed of layered Cu and a Cu3Sn portion 26G formed of layered Cu3Sn are disposed in order on the Ni plating layer 21.

[0045] Figure 5 is a partial cross-sectional view showing the layered structure of an external electrode when the Cu-based intermediate portion is a single intermediate portion, where Figure 5(a) is a partial cross-sectional view of an external electrode when an island-shaped Cu-based intermediate portion is arranged by a single intermediate portion formed by an island-shaped Cu3Sn portion, and Figure 5(b) is a partial cross-sectional view of an external electrode when a layered Cu-based intermediate portion is arranged by a single intermediate portion formed by a layered Cu3Sn portion. Figure 6 is a partial cross-sectional view showing the layered structure of an external electrode when the Cu-based intermediate portion is a composite intermediate portion, where Figure 6(a) is a partial cross-sectional view of an external electrode when an island-shaped Cu-based intermediate portion is arranged by a composite intermediate portion formed of an island-shaped Cu portion and an island-shaped Cu3Sn portion, Figure 6(b) is a partial cross-sectional view of an external electrode when a layered Cu-based intermediate portion is arranged by a composite intermediate portion formed of an island-shaped Cu portion and a layered Cu3Sn portion, and Figure 6(c) is a partial cross-sectional view of an external electrode when a layered Cu-based intermediate portion is arranged by a composite intermediate portion formed of a layered Cu portion and a layered Cu3Sn portion.

[0046] Here, the Cu portions constituting the composite intervening portion in the Cu-based intermediate portion 22 may be formed in a layered manner, as shown by Cu portion 27G in Fig. 6(c). On the other hand, the Cu portions constituting the composite intervening portion in the Cu-based intermediate portion 22 may be formed in a scattered island-like manner, as shown by Cu portion 27E in Fig. 6(a) and Cu portion 27F in Fig. 6(b).

[0047] The formation of whiskers due to thermal shock (for example, a thermal shock test under conditions of -55°C to +125°C and 30 cycles) can be effectively suppressed by providing such Cu-based intermediate portions 22. More specifically, the provision of Cu portions 27E to 27G in Cu-based intermediate portions 22E to 22G makes it possible to stably form Cu3Sn portions 26 in Cu-based intermediate portions 22E to 22G, thereby effectively suppressing the formation of whiskers.

[0048] In particular, when the Cu3Sn portion 26 of the Cu-based intermediate portion 22 is layered, the thickness t2 of the Cu3Sn portion 26 is preferably in the range of 120 nm to 460 nm, and more preferably in the range of 160 nm to 460 nm. By setting the thickness t2 of the Cu3Sn portion 26 within this range, the Cu3Sn portion 26 is formed to have a higher density than the Cu6Sn5 portion 23, which reduces the compressive stress generated in the Sn plating layer 24, thereby more effectively suppressing the formation of whiskers.

[0049] The Cu6Sn5 portion 23 is disposed on the Ni plating layer 21 directly or indirectly via the Cu-based intermediate portion 22. The electronic component 1 of this embodiment has external electrodes in which the Cu6Sn5 portion 23 is disposed directly or indirectly on the Ni plating layer 21. This improves the heat resistance of the external electrodes because the Cu6Sn5 portion 23 prevents nickel atoms from diffusing from the Ni plating layer 21 during a reflow process in which solder placed on the circuit board is heated to bond the electronic component 1 to the circuit board. As a result, mounting defects are less likely to occur when the electronic component 1 is bonded to the circuit board.

[0050] The Cu6Sn5 portion 23 is disposed in a layered form on the Ni plating layer 21 or in a scattered form on the Ni plating layer 21. Among these, the Cu6Sn5 portion 23 is preferably in a layered form. This improves the heat resistance of the external electrode 20. Furthermore, by improving the surface smoothness of the Cu6Sn5 portion 23, even when the Sn plating layer 24 described below is present, it is possible to prevent the generation of a compressive stress gradient in the Sn plating layer 24 due to the growth of Cu6Sn5 along the Sn grain boundaries. As a result, whisker growth can be more effectively suppressed. The Cu6Sn5 portion 23 may contain components other than Cu6Sn5 as additive components, and the form of the additive component is not limited.

[0051] The thickness t1 of the Cu6Sn5 portion 23 is not particularly limited, but may be, for example, in the range of 300 nm to 620 nm, preferably 400 nm to 620 nm. Here, the thickness t1 of the Cu6Sn5 portion 23 may be thicker or thinner than the thickness t2 of the Cu3Sn portion 26 of the Cu-based intermediate portion 22.

[0052] The Sn plating layer 24 is a layer disposed on the Cu6Sn5 portion 23, and is a layer disposed on the outermost layer of the external electrode 20. In particular, by providing the Sn plating layer 24 on the outermost layer of the external electrode 20, wettability with the solder used for mounting is improved when mounting the electronic component 1 on a land of a circuit board, making it easier to mount the electronic component 1 on the circuit board.

[0053] The Sn plating layer 24 is disposed so as to cover the Cu6Sn5 portion 23. The Sn plating layer 24 formed on the first external electrode 20a is disposed on the surface of the Cu6Sn5 portion 23 along the first end face 14a, and preferably extends to the surfaces of the Cu6Sn5 portion 23 along the first and second principal faces 12a and 12b and the first and second side faces 13a and 13b. The Sn plating layer 24 formed on the second external electrode 20b is disposed on the surface of the Cu6Sn5 portion 23 along the second end face 14b, and preferably extends to the surfaces of the Cu6Sn5 portion 23 along the first and second principal faces 12a and 12b and the first and second side faces 13a and 13b.

[0054] The thickness t1 of the Cu6Sn5 portion 23 and the thickness t2 of the Cu3Sn portion 26 are, for example, Analytical equipment: Scanning electron microscope (FE-SEM / EDX, FE-SEM: SU8230 / EDX: 5060FQ, manufactured by Hitachi High-Technologies Corporation) ·Magnification: 10000x The thickness of the Cu6Sn5 portion 23 can be measured by performing elemental mapping on a cross section including the thickness direction of the external electrode 20 using a color gradation method. More specifically, the Cu6Sn5 portion 23 and the Cu3Sn portion 26 are distinguished from each other by changing the color tone through elemental mapping. If they are distinguishable, the cross-sectional areas of the portions occupied by the Cu6Sn5 portion 23 and the Cu3Sn portion 26 are determined. Next, the average thickness of the Cu6Sn5 portion 23 can be calculated by dividing the obtained cross-sectional area of ​​the Cu6Sn5 portion 23 by the width along the extension direction of the Cu6Sn5 portion 23 (excluding the width of voids if the Cu6Sn5 portion 23 is island-shaped). The average thickness of the Cu3Sn portion 26 can also be calculated by dividing the obtained cross-sectional area of ​​the Cu3Sn portion 26 by the width along the extension direction of the Cu3Sn portion 26 (excluding the width of voids if the Cu3Sn portion 26 is island-shaped).

[0055] The thickness of the Sn plating layer 24 is not particularly limited, but is preferably in the range of 1 μm to 15 μm.

[0056] The electronic component 1 of this embodiment preferably has chip dimensions ranging from 01 size to 32 size. Of these, the 01 size has dimensions of 0.25 mm (length direction L) x 0.125 mm (width direction W). The 02 size has dimensions of 0.4 mm (length direction L) x 0.2 mm (width direction W). The 03 size has dimensions of 0.6 mm (length direction L) x 0.3 mm (width direction W). The 15 size has dimensions of 1.0 mm (length direction L) x 0.5 mm (width direction W). The 18 size has dimensions of 1.6 mm (length direction L) x 0.8 mm (width direction W). The 31 size has dimensions of 3.2 mm (length direction L) x 1.6 mm (width direction W). The 32 size has dimensions of 3.2 mm (length direction L) x 2.5 mm (width direction W). Therefore, the dimension of the electronic component 1 along the length direction L is preferably in the range of 0.25 mm to 3.2 mm. The dimension of the electronic component 1 along the width direction W is preferably in the range of 0.125 mm to 2.5 mm. The dimension of the electronic component 1 along the thickness direction T is not particularly limited, but can be, for example, in the range of 0.125 mm to 2.5 mm.

[0057] (2) Manufacturing methods for electronic components An example of a method for manufacturing the electronic component 1 of this embodiment will be described below using a method for manufacturing a multilayer ceramic capacitor, which is the electronic component 1 shown in Fig. 1. Note that the manufacturing method of the electronic component 1 of this embodiment is not limited as long as it satisfies the above-mentioned requirements.

[0058] First, ceramic green sheets for forming the ceramic layers 15, a conductive paste for internal electrodes for forming the internal electrode layers 16, and a conductive paste for base electrode layers for forming the base electrode layers 25 of the external electrodes 20 are prepared. Here, the ceramic green sheets, the conductive paste for internal electrodes, and the conductive paste for base electrode layers contain an organic binder and an organic solvent, and known organic binders and organic solvents can be used. Furthermore, the conductive paste for base electrode layers can contain glass or other materials in addition to metals.

[0059] Then, for example, a conductive paste for internal electrodes is printed on the ceramic green sheets in a predetermined pattern to form an internal electrode pattern on the ceramic green sheets. The conductive paste for internal electrodes can be printed by a known method such as screen printing or gravure printing.

[0060] Next, one or more ceramic green sheets are stacked in the thickness direction T on the internal electrode pattern to form a layer that will serve as the base of the ceramic layer 15, and then a conductive paste for the internal electrode is printed on top of that to form the internal electrode pattern. After repeating this process a predetermined number of times, multiple ceramic green sheets are stacked in the thickness direction T to form a layer that will serve as the base of the outer layer portion 15a, thereby producing a laminated block. If necessary, this laminated block may be pressure-bonded along the thickness direction T by means of a hydrostatic press or the like.

[0061] The laminate block is then cut to a predetermined shape and size to cut out the laminate chips. At this time, the edges and corners of the laminate chips may be rounded by barrel polishing or the like. The cut-out laminate chips are then fired to create the element body 10. The firing temperature for the laminate chips depends on the ceramic material and the material of the conductive paste for the internal electrodes, but is preferably 900°C or higher and 1300°C or lower.

[0062] Next, the first external electrode 20a is formed on the first end face 14a of the element body 10, and the second external electrode 20b is formed on the second end face 14b of the element body 10.

[0063] First, a conductive paste for the base electrode layer is applied to the surface of the fired element body 10, including the first end face 14a and the second end face 14b, and then baked to form the base electrode layer 25 on the surface of the element body 10, including the first end face 14a and the second end face 14b. The baking temperature for forming the base electrode layer 25 is preferably in the range of 700°C to 900°C. The baking of the conductive paste for the base electrode layer may be performed after forming the Ni plating layer 21 and before forming the Cu plating layer and the Sn plating layer 24. The conductive paste used to form the base electrode layer 25 may contain metal particles containing Cu or may contain metal particles containing Ni. Alternatively, the conductive paste may be baked together with the laminate chip when the laminate chip is baked to obtain the element body 10, thereby forming the base electrode layer 25 on the surface of the resulting element body 10.

[0064] Next, a Ni plating layer 21, a Cu plating layer, and a Sn plating layer 24 are sequentially formed on the base electrode layer 25, and then a heat treatment is performed to convert part or all of the Cu plating layer formed on the Ni plating layer 21 into Cu6Sn5 portions 23, or into island-shaped or layer-shaped Cu-based intermediate portions 22 and Cu6Sn5 portions 23. The temperature and time of the heat treatment for converting part or all of the Cu plating layer into the Cu6Sn5 portions 23 may be in the range of 120°C to 170°C and in the range of 30 minutes to 5 hours. Preferably, the temperature and time can be in the range of 140°C to 160°C and in the range of 1 hour to 2 hours. At this time, by adjusting the thickness of the Cu layer and the Sn layer and the heating conditions, it is possible to change from the Cu plating layer to Cu3Sn and then to Cu6Sn5 portion 23, but in addition to Cu6Sn5 portion 23, a Cu-based intermediate portion 22 having Cu3Sn portion 26 and Cu portion 27 may also be formed.

[0065] Here, the Ni plating layer 21, Cu plating layer, and Sn plating layer 24 can be formed by any known means, and are not particularly limited.

[0066] The unreacted portions of the Cu plating layer become island-like or layer-like Cu portions 27. The unreacted portions of the Sn layer become the Sn plating layer 24.

[0067] In the manner described above, a multilayer ceramic capacitor, which is the electronic component 1, is manufactured.

[0068] (3) Mounting method and structure of electronic components 7A and 7B are schematic cross-sectional views showing a mounting method of an electronic component according to this embodiment, in which FIG. 7A is a schematic cross-sectional view showing the state before solder reflow, and FIG. 7B is a schematic cross-sectional view showing the state after solder reflow after mounting on a circuit board.

[0069] The electronic component 1 of this embodiment can be mounted on the land 40 of the circuit board 4 by a known reflow process in which the electronic component 1 manufactured as described above is heated to melt the solder 5 and bond it to the circuit board.

[0070] Furthermore, in the electronic component 1 of this embodiment, as described above, the base electrode layer 25, Ni plating layer 21, Cu plating layer, and Sn plating layer 24 are sequentially formed on the surface of element body 10, including first end face 14a and second end face 14b, and the resulting structure is placed on land 40 of circuit board 4, and solder is disposed between Sn plating layer 24 and land 40. This preferably involves performing heat treatment to transform the Cu plating layer into Cu6Sn5 portion 23 or Cu-based intermediate portion 22. This reflows solder 5 on the surface of land 40, and the heat generated by this heat treatment transforms the sequentially formed base electrode layer 25, Ni plating layer 21, Cu plating layer, and Sn plating layer 24 into external electrode 20 of a desired shape. Therefore, the resulting electronic component 1 can be mounted on land 40 of circuit board 4 with external electrode 20 having desired properties during use.

[0071] By using this mounting method, the electronic component 1 of this embodiment can have a mounting structure in which an external electrode 20 having at least a Ni plating layer 21 and a Cu6Sn5 portion 23 arranged on the Ni plating layer 21 directly or indirectly via an island-shaped or layer-shaped Cu-based intervening portion is joined to a land 40 of a circuit board 4 by solder 5. [Example]

[0072] The present invention will be described in more detail using the following examples of the present invention, but the present invention is not limited to these examples.

[0073] Multilayer ceramic capacitors were fabricated as electronic components 1 according to the manufacturing method described above, and were reflow-mounted on printed circuit boards using Sn-Ag-Cu (SAC) solder. The thickness of the Cu plating layer formed on base electrode layer 25 and the heat treatment conditions were varied, and the shape of Cu portion 27 was evaluated for the resulting electronic components 1. The shape and thickness t2 (only in the case of layered structure) of Cu3Sn portion 26 and the thickness t1 of Cu6Sn5 portion 23 were measured. The resulting electronic components 1 were also evaluated for heat resistance and the presence or absence of whisker formation.

[0074] Here, the specifications of the multilayer ceramic capacitor, which is the electronic component 1, are as follows: Dimensions (design value): 3.2mm (length L) x 2.5mm (width W) x 2.5mm (thickness T) Ceramic layer 15 material: BaTiO3 Capacitance: 10μF Rated voltage: 25V Material of internal electrode layer 16: Ni External electrode structure Base electrode layer 25 Material of the base electrode layer 25: conductive metal (Cu) Thickness of the base electrode layer 25: 65 μm Thickness of Ni plating layer 21: 1.5 μm Thickness of Cu plating layer (before heat treatment): As shown in Table 1 Sn plating layer thickness (before heat treatment): 5.0 μm Presence and shape of Cu portion 27 (after heat treatment): as shown in Table 1 Thickness t2 of the layered Cu3Sn portion 26 (after heat treatment): as shown in Table 1 Thickness t1 of the layered Cu6Sn5 portion 23 (after heat treatment): as shown in Table 1

[0075] On the other hand, the multilayer ceramic capacitor of Comparative Example 1 was configured similarly to the multilayer ceramic capacitor of Example 1, except that a Sn plating layer 24 was formed without forming a Cu plating layer on the surface of the Ni plating layer 21 formed on the base electrode layer 25 on the surface of the element body 10. Here, the multilayer ceramic capacitor obtained in Comparative Example 1 did not have the Cu6Sn5 portion 23, nor did it have the Cu3Sn portion 26 or the Cu portion 27.

[0076] The heat resistance of the electronic component 1 was evaluated under the following conditions. The electronic components 1 obtained in Examples 1 to 10 of the present invention were subjected to a heat resistance test in which they were left in a thermostatic chamber at 175°C for 500 hours. Then, cross sections of the central portions of the external electrodes 20a, 20b along the thickness direction T and width direction W were observed using a scanning electron microscope (FE-SEM / EDX) (manufactured by Hitachi High-Technologies Corporation, FE-SEM: SU8230 / EDX: 5060FQ). As a result, the presence of a Ni plating layer 21 was confirmed in each of the external electrodes 20a, 20b.

[0077] Here, if the Ni plating layer 21 changes to a Ni-Sn-Cu compound during the heat resistance test and the Ni plating layer 21 covering the base electrode layer 25 is lost, the coverage rate of the Ni plating layer 21 on the base electrode layer 25 will decrease. In areas of the base electrode layer 25 that are not covered by the Ni plating layer 21, the base electrode layer 25 will come into direct contact with the Cu-based intermediate portion 22 and the Cu6Sn5 portion 23, which may cause a reaction between them, and therefore the heat resistance will likely decrease. Therefore, the length of the contact portion between the base electrode layer 25 and the Ni plating layer 21, which appears in the cross section of the central portion of the external electrode 20a along the thickness direction T and the width direction W, was determined before and after the heat resistance test. At this time, when the ratio of the area of ​​the Ni plating layer 21 covering the base electrode layer 25 after the heat resistance test (hereinafter referred to as the "covered area of ​​the Ni plating layer 21 after the heat resistance test") to the area of ​​the Ni plating layer 21 covering the base electrode layer 25 before the heat resistance test (hereinafter referred to as the "covered area of ​​the Ni plating layer 21 before the heat resistance test") exceeded 95%, it was evaluated as excellent (◎). Furthermore, when the ratio of the covered area of ​​the Ni plating layer 21 after the heat resistance test to the covered area of ​​the Ni plating layer 21 before the heat resistance test was in the range of more than 80% but less than 95%, it was evaluated as good (◯). Furthermore, when the ratio of the covered area of ​​the Ni plating layer 21 after the heat resistance test to the covered area of ​​the Ni plating layer 21 before the heat resistance test was less than 80%, it was evaluated as poor (×). The results are shown in Table 1.

[0078] In addition, the evaluation of the presence or absence of whisker formation on electronic component 1 was performed by leaving electronic components 1 obtained in Examples 1 to 10 of the present invention in a constant temperature bath at 30°C for 4000 hours, and then examining the central region, excluding a peripheral region 5 mm from the edge of the plating layer, using an SEM at a magnification of 1000x to check for the presence or absence of whiskers. Components in which no whiskers were observed were rated as excellent (◎), those in which the maximum whisker size was less than 20 μm were rated as good (○), those in which the maximum whisker size was 20 μm or more but less than 40 μm were rated as poor (△), and those in which the maximum whisker size was 40 μm or more were rated as unacceptable (×).

[0079] [Table 1]

[0080] From the results in Table 1, it can be seen that the electronic components 1 of Examples 1 to 10 of the present invention all have at least an external electrode 20 that includes a Ni plating layer 21 and a Cu6Sn5 portion 23 that is disposed directly on the Ni plating layer 21 or indirectly via an island-shaped or layer-shaped Cu-based intermediate portion 22, and the heat resistance evaluation result was evaluated as "○".

[0081] Therefore, the electronic components 1 of invention examples 1 to 10 all had external electrodes 20 with sufficient heat resistance.

[0082] On the other hand, in the electronic component of Comparative Example 1, which did not have the Cu6Sn5 portion 23 in the external electrode 20, the ratio of the coverage area of ​​the Ni plating layer 21 after the heat resistance test to the coverage area of ​​the Ni plating layer 21 before the heat resistance test was less than 80%, and the heat resistance evaluation did not reach the passing level.

[0083] The gist of the present invention may be configured as follows, for example.

[0084] <1> An electronic component comprising: an element body in which internal electrodes are embedded, the element body having a first main surface and a second main surface opposed to each other in a thickness direction, a first side surface and a second side surface opposed to each other in a width direction perpendicular to the thickness direction, and a first end surface and a second end surface opposed to each other in a length direction perpendicular to both the thickness direction and the width direction; and a pair of external electrodes disposed at least on the first end surface and the second end surface of the element body and connected to the internal electrodes, the external electrodes comprising a Ni plating layer and a Cu-based intervening portion disposed on the Ni plating layer directly or indirectly via an island-shaped or layer-shaped Cu-based intervening portion. 6 Sn 5 An electronic component having at least a portion.

[0085] <2> The Cu-based intervening portion is formed by depositing island-shaped or layer-shaped Cu on the Ni plating layer. 3 A single intervening part formed of Sn, or a Cu part formed of island-like or layered Cu, and an island-like or layered Cu 3 Cu formed with Sn 3 The composite interposition portion is formed by sequentially arranging a Sn portion and a <1> The electronic component according to claim 1.

[0086] <3> Cu 6 Sn 5 The thickness of the Cu 3 The thickness of the Sn part is thicker than the above. <2> The electronic component according to claim 1.

[0087] <4> Cu 3 The thickness of the Sn portion is in the range of 120 nm to 460 nm. <2> or <3> The electronic component according to claim 1.

[0088] <5> The Cu portion constituting the composite interposition portion is formed in a layer shape. <2> from <4> 10. The electronic component according to claim 9 .

[0089] <6> The Cu portion constituting the composite interposition portion is formed in an island-like scattered manner. <2> from <4> 10. The electronic component according to claim 9 .

[0090] <7> Cu 6 Sn 5 The thickness of the part is in the range of 300 nm to 620 nm. <1> from <6> 10. The electronic component according to claim 9 .

[0091] <8> the above <1> from <7> 1. A mounting method for mounting the electronic component according to any one of claims 1 to 9 on a land of a circuit board, comprising: The external electrodes are formed by sequentially forming a Ni plating layer, a Cu plating layer, and an Sn plating layer on a base electrode layer, and then by performing a heat treatment to partially or entirely convert the Cu plating layer formed on the Ni plating layer into a Cu plating layer. 6 Sn 5 The Cu-based intervening part and the Cu-based intervening part are changed into island-like or layer-like. 6 Sn 5 A method for mounting electronic components, comprising the step of changing the mounting part into a part.

[0092] <9> The heat treatment is performed after solder is placed between the external electrodes and the lands. <8> 2. A mounting method for an electronic component according to claim 1.

[0093] <10> the above <1> from <7> A mounting structure in which the electronic component according to any one of claims 1 to 4 is mounted on a land of a circuit board, The electronic component is made of a Ni-plated layer and a Cu-based intervening portion disposed on the Ni-plated layer directly or indirectly via an island-shaped or layer-shaped Cu-based intervening portion. 6 Sn 5 and the external electrode having at least a portion is joined to the land of the circuit board by soldering. [Explanation of symbols]

[0094] 1. Electronic components (multilayer ceramic capacitors) 4 Circuit Board 5 Solder 10 Base 12a First principal surface 12b Second main surface 13a First Aspect 13b Second Aspect 14a first end face 14b second end face 15 ceramic layers 15a Outer layer 15b Inner layer 16 Internal electrode layer 16a First internal electrode layer 16b Second internal electrode layer 17a first opposing electrode portion 17b Second opposing electrode portion 18a First extraction electrode portion 18b Second extraction electrode portion 19a Separation section (L gap) 19b Separation part (W gap) 20a First external electrode 20b Second external electrode 21 Ni plating layer 22 Cu-based intervening part 23 Cu6Sn5 part 24 Sn plating layer 25 Base electrode layer 26 Cu3Sn part 27 Cu part 40 rand L lengthwise T thickness direction W width direction Thickness of t1Cu6Sn5 part Thickness of t2Cu3Sn part

Claims

1. an element body having internal electrodes embedded therein, the element body having a first main surface and a second main surface opposed to each other in a thickness direction, a first side surface and a second side surface opposed to each other in a width direction perpendicular to the thickness direction, and a first end surface and a second end surface opposed to each other in a length direction perpendicular to both the thickness direction and the width direction; a pair of external electrodes disposed on at least the first end face and the second end face of the element body and connected to the internal electrodes; An electronic component comprising: The external electrode is a Ni plating layer; Cu is disposed directly on the Ni plating layer or indirectly via an island-shaped or layer-shaped Cu-based intervening portion. ６ Sn ５ Part and and The Cu-based intervening portion is On the Ni plating layer, A Cu portion formed of layered Cu and an island-shaped or layered Cu ３ Cu formed with Sn ３ The electronic component is a composite interposed portion formed by sequentially arranging a Sn portion and a Sn portion.

2. The Cu ６ Sn ５ The thickness of the Cu ３ The electronic component according to claim 1 , wherein the thickness of the Sn portion is greater than the thickness of the Sn portion.

3. The Cu ３ 2. The electronic component according to claim 1, wherein the Sn portion has a thickness in the range of 120 nm to 460 nm. 。

4. The Cu ６ Sn ５ The electronic component according to claim 1 , wherein the thickness of the portion is in the range of 300 nm to 620 nm.

5. A mounting method for mounting the electronic component according to claim 1 on a land of a circuit board, comprising the steps of: The external electrodes are formed by sequentially forming a Ni plating layer, a Cu plating layer, and an Sn plating layer on a base electrode layer, and then by performing heat treatment to partially or entirely convert the Cu plating layer formed on the Ni plating layer into a Cu plating layer. ６ Sn ５ or island-like or layer-like Cu-based intervening parts and Cu ６ Sn ５ A method for mounting electronic components, comprising the step of changing the mounting part into a part.

6. 6. The electronic component mounting method according to claim 5, wherein the heat treatment is performed after solder is placed between the external electrodes and the lands.

7. A mounting structure in which the electronic component according to claim 1 is mounted on a land of a circuit board, The electronic component comprises a Ni-plated layer and a Cu-based intervening portion disposed on the Ni-plated layer directly or indirectly via an island-shaped or layer-shaped Cu-based intervening portion. ６ Sn ５ The Cu-based intervening portion has at least a Cu portion formed of layered Cu on the Ni plating layer, and an island-shaped or layered Cu portion. ３ Cu formed with Sn ３ the external electrode, which is a composite interposed portion formed by sequentially arranging a Sn portion and a Sn portion, is joined to the land of the circuit board by soldering.

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