Electronic component mounting structure

Abstract

When the mounting structure of the electronic component is exposed to a high temperature, the bonding strength of the electronic component to the land of the substrate may be reduced depending on the type of alloy generated in the solder bonding portion.SOLUTION: The electronic component mounting structure 100 includes the substrate 90 having the land 92, the capacitor component 10 having the first outer electrode 60 laminated on the outer surface of the element body 20, and the solder 80 containing Sn and Bi. The first external electrode 60 is bonded to the land 92 by the solder 80. At least one selected from the land 92 and the first external electrode 60 contains Ni. One or more selected from the land 92, the first external electrode 60, and the solder 80 contain Au, and one or more selected from the land 92, the first external electrode 60, and the solder 80 contain Cu. An alloy portion containing Sn, Cu, Au, and Ni is further provided in a region adjacent to the solder 80.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a mounting structure for electronic components. [Background technology]

[0002] Patent Document 1 discloses a structure in which a multilayer ceramic capacitor is mounted on a land of a substrate by soldering. The multilayer ceramic capacitor of Patent Document 1 includes a dielectric layer, a plurality of internal electrode layers, and external electrodes. Each internal electrode extends inside the dielectric layer. An end of each internal electrode is exposed from the surface of the dielectric layer. The external electrodes are laminated on the surface of the dielectric layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-111361 Summary of the Invention [Problem to be solved by the invention]

[0004] In the mounting structure of electronic components as described in Patent Document 1, for example, exposure to high heat or the passage of time can cause the metal components contained in the lands of the board to alloy with the metal components contained in the solder. Depending on the type of alloy thus formed, this can cause a decrease in the bonding strength of the electronic component to the terminals of the board. [Means for solving the problem]

[0005] In order to solve the above problems, there is provided a mounting structure for an electronic component comprising: a substrate having lands; an electronic component having an element body and external electrodes laminated on the outer surface of the element body; and solder containing Sn and Bi, wherein the external electrodes are joined to the lands with the solder; one or more selected from the lands and the external electrodes contain Ni; one or more selected from the lands, the external electrodes, and the solder contain Au; and one or more selected from the lands, the external electrodes, and the solder contain Cu; and the mounting structure for an electronic component further comprises an alloy portion containing Sn, Cu, Au, and Ni in a region adjacent to the solder. [Effects of the Invention]

[0006] According to the present invention, it is possible to suppress a decrease in the bonding strength of the electronic component to the land of the substrate. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a partial cross-sectional perspective view of a capacitor component. [Figure 2] FIG. 2 is a partial cross-sectional view of a mounting structure for a capacitor component. [Figure 3] FIG. 3 is a schematic diagram showing the substrate preparation step. [Figure 4] FIG. 4 is a schematic diagram showing the solder application step. [Figure 5] FIG. 5 is a schematic diagram showing the mounting process. [Figure 6] FIG. 6 is a schematic diagram showing the heating step. [Figure 7] FIG. 7 is a graph showing the results of an impact resistance test of the capacitor component. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment in which the present invention is applied to a capacitor component 10 as an electronic component will be described below with reference to the drawings. Note that the drawings may show components enlarged to facilitate understanding. The dimensional ratios of the components may differ from those in the actual product or from those in other drawings.

[0009] <About capacitor components> As shown in Fig. 1, the capacitor component 10 is a multilayer ceramic capacitor. The capacitor component 10 includes an element body 20. Note that Fig. 1 illustrates the capacitor component 10 with a portion thereof virtually cut away in order to show the internal structure. The element body 20 has a rectangular parallelepiped shape and has a central axis CA.

[0010] In the following description, an axis extending along the central axis CA is referred to as the first axis X. One of the axes perpendicular to the first axis X is referred to as the second axis Y. An axis perpendicular to the first axis X and the second axis Y is referred to as the third axis Z. One of the directions along the first axis X is referred to as the first positive direction X1, and the direction along the first axis X opposite to the first positive direction X1 is referred to as the first negative direction X2. One of the directions along the second axis Y is referred to as the second positive direction Y1, and the direction along the second axis Y opposite to the second positive direction Y1 is referred to as the second negative direction Y2. One of the directions along the third axis Z is referred to as the third positive direction Z1, and the direction along the third axis Z opposite to the third positive direction Z1 is referred to as the third negative direction Z2.

[0011] The outer surface of element body 20 has six flat surfaces 22. Note that the "surface" of element body 20 here refers to what can be observed as a surface when the entire element body 20 is observed. In other words, even if there are minute irregularities or steps that cannot be seen unless a part of element body 20 is magnified and observed using a microscope or the like, the surface is expressed as a flat surface or a curved surface.

[0012] The six flat surfaces 22 face in different directions. The six flat surfaces 22 are roughly divided into a first end surface 22A facing the first positive direction X1, a second end surface facing the first negative direction X2, and four side surfaces 22C adjacent to each end surface. The four side surfaces 22C are a surface facing the third positive direction Z1, a surface facing the third negative direction Z2, a surface facing the second positive direction Y1, and a surface facing the second negative direction Y2, respectively.

[0013] As shown in FIG. 1, the dimension of element body 20 along the first axis X is greater than the dimension along the second axis Y and the dimension along the third axis Z. The material of element body 20 is a dielectric ceramic. Specifically, the material of element body 20 is mainly composed of BaTiO3. The term "main component" refers to a material containing a target substance in an amount exceeding 50%. For example, the content of BaTiO3 in element body 20 exceeds 50 mol%. The material of element body 20 may be mainly composed of CaTiO3, SrTiO3, CaZrO3, etc. The material of element body 20 may also contain, as a secondary component, a Mn compound, a Co compound, a Si compound, or a compound containing a rare earth element, etc.

[0014] As shown in Fig. 1, the capacitor component 10 includes five first internal electrodes 41 and four second internal electrodes 42. The first internal electrodes 41 and the second internal electrodes 42 are embedded inside the element body 20. Note that in Fig. 1, only some of the first internal electrodes 41 are denoted by reference numerals. The same applies to the second internal electrodes 42.

[0015] The material of the first internal electrode 41 is a conductive material. Specifically, the material of the first internal electrode 41 is Ni. The material of the second internal electrode 42 is the same as the material of the first internal electrode 41.

[0016] The first internal electrode 41 has a rectangular plate shape. The main surface of the first internal electrode 41 is perpendicular to the third axis Z. 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 third axis Z, similar to the first internal electrode 41. Note that the main surface here refers to the flat surface with the largest area among the outer surfaces of a plate-shaped object.

[0017] The dimension of the first internal electrode 41 in the direction along the first axis X is smaller than the dimension of the element body 20 in the direction along the first axis X. The dimensions of the second internal electrode 42 in each direction are approximately the same as those of the first internal electrode 41.

[0018] 1, the first internal electrodes 41 and the second internal electrodes 42 are positioned alternately in the direction along the third axis Z. That is, from the side surface 22C facing the third positive direction Z1 toward the third negative direction Z2, the first internal electrode 41, the second internal electrode 42, the first internal electrode 41, and the second internal electrode 42 are arranged in this order. In this embodiment, the distances between the internal electrodes in the direction along the third axis Z are equal.

[0019] As shown in Fig. 1, the five first internal electrodes 41 and the four second internal electrodes 42 are all located at the center of the element body 20 in the direction along the second axis Y. On the other hand, as shown in Fig. 1, the first internal electrodes 41 are biased toward the first positive direction X1. Although not shown, the second internal electrodes 42 are biased toward the first negative direction X2.

[0020] Specifically, as shown in FIG. 1 , the end of the first internal electrode 41 on the first positive direction X1 side coincides with the end of the element body 20 on the first positive direction X1 side. Therefore, the end of the first internal electrode 41 on the first positive direction X1 side is exposed at the first end surface 22A. The end of the first internal electrode 41 on the first negative direction X2 side is located inside the element body 20 and does not reach the end of the element body 20 on the first negative direction X2 side. On the other hand, although not shown, the end of the second internal electrode 42 on the first negative direction X2 side coincides with the end of the element body 20 on the first negative direction X2 side. Therefore, the end of the second internal electrode 42 on the first negative direction X2 side is exposed at the second end surface. The end of the second internal electrode 42 on the first positive direction X1 side is located inside the element body 20 and does not reach the end of the element body 20 on the first positive direction X1 side.

[0021] As shown in FIG. 1, the capacitor component 10 includes a first external electrode 60 and a second external electrode 61. The first external electrode 60 covers the first end face 22A of the element body 20 and portions of the four side faces 22C facing the first positive direction X1. That is, the first external electrode 60 is a five-sided electrode. As shown in FIG. 2, the first external electrode 60 has a first base electrode layer 60A, a first Ni layer 60B, a first Cu layer 60C, and a first Sn layer 60D. The first base electrode layer 60A, the first Ni layer 60B, the first Cu layer 60C, and the first Sn layer 60D are stacked in this order from the outer surface side of the element body 20. Note that FIG. 2 does not show the internal electrodes inside the element body 20.

[0022] The first base electrode layer 60A is laminated on a portion of the outer surface of the element body 20, including the first end face 22A. Specifically, the first base electrode layer 60A covers the first end face 22A and portions of the four side faces 22C of the element body 20 facing the first positive direction X1. In this embodiment, the first base electrode layer 60A is made of Cu. The first base electrode layer 60A may contain a polymer compound made of inorganic carbon and organic carbon.

[0023] The first Ni layer 60B is laminated on the first base electrode layer 60A. That is, the first Ni layer 60B covers the first base electrode layer 60A from the outside. The first Ni layer 60B is mainly composed of Ni. The first Ni layer 60B is formed by, for example, electrolytic plating of Ni.

[0024] The first Cu layer 60C is stacked on the first Ni layer 60B. That is, the first Cu layer 60C covers the first Ni layer 60B from the outside. The first Cu layer 60C covers 80% or more of the outer surface of the first Ni layer 60B. In this embodiment, the first Cu layer 60C covers substantially the entire first Ni layer 60B. Note that the thickness of the first Cu layer 60C may be locally zero. However, when calculating the above ratio, we will not take into account parts of the first Cu layer 60C where the thickness is zero and which cannot be observed without a microscope. That is, we will calculate the above ratio based on the overlapping area between the area surrounded by the outer edges of the first Cu layer 60C and the area surrounded by the outer edges of the first Ni layer 60B.

[0025] The first Cu layer 60C is primarily composed of Cu. The first Cu layer 60C is formed, for example, by electrolytic plating of Cu. The average thickness T1 of the first Cu layer 60C is less than 6 μm. The average thickness T1 of the first Cu layer 60C in the first external electrode 60 is calculated as follows: First, a cross section of the first Cu layer 60C including the inner surface on the element body 20 side and the outer surface on the opposite side, which is perpendicular to the outer surface of the element body 20, is photographed using an electron microscope. Next, a measurement range is identified in the photographed image in a direction along the outer surface of the first Ni layer 60B. The measurement range is 10 μm or more. The measurement range may be continuous and 10 μm or more, or the total of multiple ranges at different locations may be 10 μm or more. The cross-sectional area of ​​the first Cu layer 60C in the measurement range is then calculated by image processing. Next, the average thickness T1 of the first Cu layer 60C in the first external electrode 60 is determined by dividing the calculated cross-sectional area of ​​the first Cu layer 60C in the measurement range by the length of the measurement range.

[0026] The first Sn layer 60D is laminated on the first Cu layer 60C. That is, the first Sn layer 60D covers the first Cu layer 60C from the outside. The first Sn layer 60D is mainly composed of Sn. The first Sn layer 60D is formed by, for example, electrolytic plating of Sn.

[0027] The second external electrode 61 covers the second end face of the element body 20 and parts of the four side faces 22C facing the first negative direction X2. That is, the second external electrode 61 is a five-sided electrode. The second external electrode 61 does not reach the first external electrode 60 on the side face 22C, and is spaced apart from the first external electrode 60 in the direction along the first axis X. Furthermore, the first external electrode 60 and the second external electrode 61 are not stacked in the central part of the side face 22C of the element body 20 in the direction along the first axis X.

[0028] Although not shown, the second external electrode 61 has a second base electrode layer, a second Ni layer, a second Cu layer, and a second Sn layer. The configurations of the second base electrode layer, second Ni layer, second Cu layer, and second Sn layer of the second external electrode 61 are similar to the configurations of the first base electrode layer 60A, first Ni layer 60B, first Cu layer 60C, and first Sn layer 60D of the first external electrode 60. The average thickness of the second Cu layer is less than 6 μm, and preferably 0.5 μm or more and 2 μm or less.

[0029] <About the mounting structure of capacitor components> Next, a description will be given of a mounting structure 100 between the capacitor component 10 and the substrate 90. Note that, although a mounting structure between the first external electrode 60 of the capacitor component 10 and the substrate 90 will be described below, the same applies to a mounting structure between the second external electrode 61 and the substrate 90.

[0030] As shown in FIG. 2, the substrate 90 has a substrate body 91 and lands 92. The substrate body 91 is made of an insulating material such as synthetic resin. The substrate body 91 is plate-shaped. The lands 92 are laminated on the main surface of the substrate body 91. The lands 92 are portions for mounting the capacitor component 10 described above. Although not shown in the figure, the lands 92 are connected to wiring or the like extending on the substrate body 91.

[0031] Before the capacitor component 10 is mounted, the land 92 has an underlayer 93, a first plating layer 94, and a second plating layer. The underlayer 93, the first plating layer 94, and the second plating layer are stacked in this order from the substrate body 91 side. The underlayer 93 is primarily composed of Cu. The first plating layer 94 is primarily composed of Ni. The second plating layer is primarily composed of Au. These layers may contain elements other than the primary components. During the solder joining process, most of the Au in the second plating layer dissolves into the solder 80. Therefore, the clear second plating layer becomes invisible due to the joining by the solder 80.

[0032] 2, the capacitor component 10 is bonded to a land 92 of a substrate 90 via solder 80. Specifically, when the capacitor component 10 is mounted on the land 92 of the substrate 90, one surface of the first external electrode 60 of the capacitor component 10 faces the land 92. In this embodiment, the surface of the first external electrode 60 facing the third negative direction Z2 faces the land 92. A portion of the solder 80 is interposed between the land 92 and the first external electrode 60 facing the land 92.

[0033] The solder 80 is in contact with the surface of the first external electrode 60 facing the first positive direction X1. Although not shown, the solder 80 is also in contact with the surface of the first external electrode 60 facing the second positive direction Y1 and the surface of the first external electrode 60 facing the second negative direction Y2. The solder 80 has a shape that expands outward as it approaches the substrate 90, a so-called fillet shape.

[0034] The solder 80 contains Sn and Bi. As described above, the first external electrode 60 has the first Sn layer 60D as its outermost layer. Therefore, the solder 80 is configured as an integral part of the first Sn layer 60D with no clear boundary therebetween. For convenience, in FIG. 2, the fillet-shaped portion indicated by the dashed line is designated as the solder 80.

[0035] The mounting structure 100 has a first alloy part 70A and a second alloy part 70B. The term "alloy" as used herein encompasses intermetallic compounds, solid solutions, and eutectic states. Both the first alloy part 70A and the second alloy part 70B are located in a region adjacent to the solder 80. The first alloy part 70A is an alloy containing Sn, Cu, Au, and Ni. In this embodiment, each of the above metal components originates from a metal component contained in any of the first external electrode 60, the solder 80, and the land 92. The metal components constituting the second alloy part 70B and the origin of the above metal components are the same as those of the first alloy part 70A.

[0036] First alloy portion 70A is located in the region between first plating layer 94 of land 92 and solder 80. First alloy portion 70A is in the form of a layer along the main surface of land 92. First alloy portion 70A extends over the entire main surface of land 92. Note that this shape results from solder 80 wetting and spreading over the entire main surface of land 92 during the manufacturing process for producing mounting structure 100.

[0037] The second alloy part 70B is located in a region between the first external electrode 60 and the solder 80. In this embodiment, not only the surface of the first external electrode 60 facing the third negative direction Z2 but also a portion of the surface facing the first positive direction X1 is in contact with the solder 80. More specifically, of the surface facing the first positive direction X1, a portion on the third negative direction Z2 side is in contact with the solder 80. Although not shown, a portion of the surface of the first external electrode 60 facing the second positive direction Y1 on the third negative direction Z2 side and a portion of the surface facing the second negative direction Y2 on the third negative direction Z2 side are also in contact with the solder 80. Reflecting this positional relationship between the first external electrode 60 and the solder 80, the second alloy part 70B is present on the entire surface of the first external electrode 60 that is in contact with the solder 80.

[0038] The average thickness Tb of the second alloy portion 70B is greater than the average thickness Ta of the first alloy portion 70A. Specifically, the average thickness Tb of the second alloy portion 70B is 1.5 to 6 times the average thickness Ta of the first alloy portion 70A. The average thickness of each alloy portion can be calculated in the same manner as the average thickness T1 of the first Cu layer 60C in the first outer electrode 60.

[0039] <About the manufacturing method of the mounting structure> The manufacturing method of the mounting structure 100 includes a substrate preparation step, a solder application step, a mounting step, and a heating step.

[0040] First, a substrate preparation step is performed as shown in FIG. 3. In the substrate preparation step, a substrate 90 is placed in a predetermined position. The substrate 90 has a pair of lands 92 for each capacitor component 10 to be mounted. The pair of lands 92 are arranged at a distance from each other in a direction parallel to the main surface of the substrate body 91. The distance between the pair of lands 92 is shorter than the distance from the first end face 22A to the second end face of the capacitor component 10 in the direction along the first axis X. The area of ​​the main surface of each land 92 is larger than the area of ​​the surface of the first external electrode 60 of the capacitor component 10 facing the third negative direction Z2.

[0041] Next, as shown in FIG. 4, a solder application process is performed. In the solder application process, a solder paste containing solder 80 is applied onto each land 92 on the substrate 90. In this embodiment, the solder paste containing solder 80 is applied to the entire main surface of each land 92. The solder paste is made by mixing and stirring solder particles made of Sn-58Bi, which are the basis of the solder 80, with flux, a thixotropic agent, and the like. The solder particle size has a median diameter of 3 μm or more and 60 μm or less. The flux content is 5 wt% or more and 20 wt% or less of the total weight.

[0042] Next, a mounting process is performed as shown in Fig. 5. In the mounting process, the capacitor component 10 is placed on a pair of lands 92. Specifically, the first external electrode 60 is placed on the main surface of one of the lands 92, and the second external electrode 61 is placed on the main surface of the other land 92. As described above, the solder paste containing the solder 80 has already been applied to each land 92, so when the capacitor component 10 is placed in the mounting process, the solder 80 is present between each land 92 and the capacitor component 10.

[0043] Next, as shown in FIG. 6, a heating step is performed. In the heating step, the solder 80 is heated to melt it. Specifically, the entire substrate 90 and capacitor component 10 are heated in a heating furnace. The heating temperature is set to a temperature at which the solder 80 melts without thermally damaging the substrate 90 and capacitor component 10. When the solder 80 melts, it spreads over the surfaces of the first external electrode 60 facing the first positive direction X1, the second positive direction Y1, and the second negative direction Y2. As a result, the solder 80 forms a fillet shape. The same applies to the second external electrode 61.

[0044] <About the comparative test> The results of tests on the impact resistance of capacitor components are described below. Samples A, B, C, D, and E of the mounting structures described below were subjected to the tests. Unless otherwise specified, the structures and materials of these samples conform to the structure and materials of the mounting structure 100 of the above embodiment. Sample A was also prepared for comparison.

[0045] As shown in FIG. 7, the solder material is Sn-58Bi in Samples A, B, C, D, and E. Of Samples A, B, C, D, and E, each external electrode of the capacitor component has a Cu layer. In other words, in Sample A, each external electrode of the capacitor component does not have a Cu layer. In Sample B, the average thickness of the Cu layer on each external electrode is 0.5 μm. In Sample C, the average thickness of the Cu layer on each external electrode is 1 μm. In Sample D, the average thickness of the Cu layer on each external electrode is 2 μm. In Sample E, the average thickness of the Cu layer on each external electrode is 6 μm.

[0046] In this comparative test, samples A, B, C, D, and E were exposed to an atmosphere at 125°C for 500 hours. After that, the impact resistance of the capacitor components on the board was examined for samples A, B, C, D, and E. Similarly, the impact resistance of the capacitor components on the board in the initial state was examined for samples A, B, C, D, and E. Here, the "initial state" refers to the state before each mounting structure was exposed to an atmosphere at 125°C. There were 16 specimens for each sample.

[0047] The method for evaluating impact resistance in this comparative test will now be described. Impact resistance in this comparative test was evaluated using a so-called pendulum impact test. Specifically, a board on which capacitor components were mounted was attached to a pendulum impact tester so that the first external electrode 60 swung downward from the third negative direction Z2 to the third positive direction Z1 in FIG. 2. The impact generated by operating and suddenly stopping the attached pendulum was applied 1,000 times to each of 16 samples of the same type. The percentage of these 16 samples in which the capacitor components remained without falling off was used as an index of impact resistance.

[0048] If a capacitor component fell off in a specific sample before the number of drop impacts reached 1000, the test for that sample was terminated at that stage. If capacitor components fell off in all 16 samples of the same type before the number of drop impacts reached 1000, the number of times that the capacitor component fell off in the last sample was used as an index of impact resistance.

[0049] According to this comparative test, the impact resistance of samples A, B, C, D, and E in the initial state is as shown by the dashed lines in Figure 7. Specifically, sample A had an impact resistance of 44%. sample B had an impact resistance of 56%. sample C had an impact resistance of 69%. sample D had an impact resistance of 56%. sample E had an impact resistance of 63%. Thus, when the external electrodes of the capacitor component had a Cu layer, impact resistance was significantly improved compared to when the external electrodes did not have a Cu layer.

[0050] On the other hand, the impact resistance of Samples A, B, C, D, and E exposed to an atmosphere at 125°C for 500 hours is shown by the solid line in Figure 7. Specifically, for Sample A, all 16 capacitor components fell off after 200 drop impacts. For Sample B, the impact resistance was 25%. For Sample C, the impact resistance was 50%. For Sample D, the impact resistance was 69%. For Sample E, all 16 capacitor components fell off after 400 drop impacts. Thus, when the external electrodes of the capacitor components had a Cu layer, the deterioration of impact resistance due to high heat was suppressed compared to when the external electrodes did not have a Cu layer. Furthermore, some of Samples B to D were able to withstand the pendulum impact test even after exposure to high temperatures. Therefore, it was found that the average thickness of the Cu layer is particularly preferably 0.5 μm or more and 2 μm or less.

[0051] Furthermore, when the external electrodes did not have a Cu layer, the bond between the capacitor component and the land, which was closer to the substrate, was destroyed when the capacitor component fell off, whereas when the external electrodes had a Cu layer, the second alloy portion or its vicinity was destroyed when the capacitor component fell off.

[0052] <Effects of the embodiment> The effects of this embodiment will be described. (1) In the above embodiment, the external electrodes of the capacitor component 10 and the lands 92 of the substrate 90 contain Ni components. Furthermore, the lands 92 contain Au components. Therefore, when the substrate 90 and the capacitor component 10 are exposed to high temperatures or temperature changes, alloys of the above components and the Sn contained in the solder 80 are formed. Specifically, an alloy of the Ni component and the Sn contained in the solder 80, and an alloy of the Ni, Sn, and Au are formed. Because the Ni-Sn alloy and the Ni-Sn-Au alloy are more brittle than the solder 80, the formation of such alloy layers reduces the bonding strength of the capacitor component 10 to the substrate 90.

[0053] In this regard, the presence of a Cu layer in each external electrode results in the formation of a Ni-Sn-Au-Cu alloy. The Ni-Sn-Au-Cu alloy has higher strength than Ni-Sn and Ni-Sn-Au alloys. Meanwhile, the presence of Cu in each external electrode and the land 92 suppresses the formation of Ni-Sn and Ni-Sn-Au alloys. Therefore, according to the above embodiment, a decrease in the bonding strength between the land 92 and the capacitor component 10 is suppressed.

[0054] (2) In the above embodiment, a Ni-Sn-Au-Cu alloy is present in the region between the land 92 and the solder 80 and in the region between the solder 80 and each external electrode. These regions are both boundaries between the solder and other objects, making them prone to solder peeling. Furthermore, these regions are prone to migration of components such as Ni and Au from the land 92 and each external electrode. In other words, these regions are not only weak in bonding strength, but are also prone to the formation of Ni-Sn and Ni-Sn-Au alloys, which can reduce bonding strength. The presence of a Ni-Sn-Au-Cu alloy in these regions is particularly advantageous for preventing a reduction in bonding strength between the capacitor component 10 and the land 92.

[0055] (3) In the above embodiment, the average thickness Tb of the second alloy portion 70B is greater than the average thickness Ta of the first alloy portion 70A. This prevents the substrate 90 from being destroyed. If the capacitor component 10 were to fall off, it is more likely that the fall-off would be caused by destruction of the second alloy portion 70B rather than the substrate 90. By intentionally making the substrate 90 more susceptible to destruction on the side farther from the land 92, even if destruction were to occur between the capacitor component 10 and the substrate 90, the effects of the destruction would be prevented from reaching the substrate 90.

[0056] (4) As in the above embodiment, since each external electrode contains Cu, the average thickness Tb of the second alloy portion 70B is likely to be larger than the average thickness Ta of the first alloy portion 70A when manufacturing the mounting structure 100. Therefore, the above relationship in the average thickness of each alloy portion can be achieved without employing a special manufacturing process for increasing the average thickness Tb of the second alloy portion 70B.

[0057] (5) According to this comparative test, when the first Cu layer 60C of the external electrode is 6 μm thick, the bonding strength of the capacitor component 10 to the substrate 90 is lower than when the first Cu layer 60C is 2 μm thick. That is, when the average thickness T1 of the first Cu layer 60C is 6 μm or greater, the effect of suppressing the decrease in bonding strength decreases. Furthermore, the greater the average thickness T1 of the first Cu layer 60C, the greater the overall thickness of each external electrode, which results in a larger size of the capacitor component 10. Therefore, from the viewpoint of preventing the size of the capacitor component 10 from increasing while still obtaining the effects of the first Cu layer 60C, it is preferable that the thickness of the first Cu layer 60C be less than 6 μm.

[0058] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0059] The shape of the element body 20 is not limited to a rectangular parallelepiped. The first external electrode 60 is not limited to a five-sided electrode as shown in the example of the above embodiment. For example, there may be a side surface 22C on which the first external electrode 60 is not arranged. For example, the first external electrode 60 does not have to be arranged on the first end surface 22A. Regardless of the shape of the first external electrode 60, it is sufficient that electrical connection between the land 92 and the capacitor component 10 is ensured. The same applies to the second external electrode 61.

[0060] In the above embodiment, an example was shown in which a capacitor component 10 was used as the electronic component, but the type of electronic component is not limited to a multilayer ceramic capacitor. Any electronic component having an element body 20 and external electrodes may be used. Examples of this type of electronic component include piezoelectric components, thermistors, and inductors. Furthermore, the element body 20 of the electronic component is not limited to being made of a dielectric material, and may be made of, for example, a magnetic material, a piezoelectric material, or a magnetic metal material.

[0061] The number of first internal electrodes 41 and second internal electrodes 42 is not limited to the example in the above embodiment. The number of first internal electrodes 41 may be more or less than five. The same applies to the second internal electrodes 42.

[0062] The material of the solder 80 is not limited to Sn-58Bi as long as it contains Sn and Bi. For example, the solder 80 may contain one or more elements selected from Pb, Ag, and Cu in addition to Sn and Bi.

[0063] The main components of the first plating layer 94 and the second plating layer of the land 92 are not limited to the example of this embodiment. The main component of the first plating layer 94 does not have to be Ni. Furthermore, the main component of the second plating layer does not have to be Au. It is sufficient that electrical connection between the land 92 and the electronic component is ensured. However, if the land 92, the solder 80, or the first external electrode 60 contains Ni and Au, an alloy of Sn, Ni, and Au may be generated, which may result in a decrease in bonding strength.

[0064] The main component of the underlayer 93 of the land 92 is not limited to the example of this embodiment. The material of the first external electrode 60 is not limited. The first external electrode 60 may have a one-layer structure, a two-layer structure, or a multi-layer structure of five or more layers. The same applies to the second external electrode 61.

[0065] In the above embodiment, an example was shown in which each external electrode contains Cu, but instead of each external electrode, the solder 80 or the land 92 may contain Cu. Also, an example was shown in which the main component of the second plating layer of the land 92 is Au, but instead of the land 92, the solder 80 or each external electrode may contain Au. In other words, if any of the external electrodes, the land 92, or the solder 80 contains Cu and Au, an alloy portion containing Sn, Cu, Au, and Ni may be generated.

[0066] The average thickness T1 of the first Cu layer 60C of the first external electrode 60 may be 6 μm or more. This also applies to the second external electrode 61. The average thickness Tb of the second alloy portion 70B may be smaller than the average thickness Ta of the first alloy portion 70A.

[0067] The solder 80 does not have to spread over the entire main surface of the land 92. It is sufficient that electrical connection between the land 92 and the capacitor component 10 is ensured. The same applies to the second external electrode 61.

[0068] There does not have to be a fillet shape. For example, the solder 80 does not have to have a clear fillet shape. Furthermore, the area of ​​the main surface of the land 92 may be smaller than the area of ​​the surface of the first external electrode 60 that faces the main surface of the land 92.

[0069] Each alloy portion does not necessarily have to be in a layered form. The alloy portion may be embedded within the solder 80 or may be exposed to the outside of the solder 80. As long as the alloy portion is present in a region adjacent to the solder 80 in this way, the formation of the brittle alloy exemplified in the above embodiment can be suppressed regardless of the shape of the alloy portion.

[0070] <Additional Notes> The technical ideas that can be understood from the above-described embodiment and modified examples will be described. [1] A mounting structure for an electronic component comprising: a substrate having lands; an electronic component having an element body and external electrodes laminated on the outer surface of the element body; and solder containing Sn and Bi, wherein the external electrodes are joined to the lands with the solder; one or more selected from the lands and the external electrodes contain Ni; one or more selected from the lands, the external electrodes, and the solder contain Au; and one or more selected from the lands, the external electrodes, and the solder contain Cu; and further comprising an alloy portion containing Sn, Cu, Au, and Ni in a region adjacent to the solder.

[0071] [2] The electronic component mounting structure according to [1], wherein the alloy portion is located in one or more areas selected from the area between the land and the solder and the area between the land and the solder.

[0072] [3] The mounting structure of an electronic component described in [1] or [2], wherein the alloy portion comprises a first alloy portion located in the region between the land and the solder, and a second alloy portion located in the region between the solder and the external electrode.

[0073] [4] The electronic component mounting structure according to any one of [1] to [3], wherein the second alloy portion has a larger average thickness than the first alloy portion. [5] The electronic component mounting structure according to any one of [1] to [4], wherein the external electrodes contain Cu.

[0074] [6] The mounting structure of an electronic component according to any one of [1] to [5], wherein the element body is rectangular, and the external electrodes are arranged on one or more planes selected from one end face and four side faces adjacent to the end face among six planes constituting the outer surface of the element body.

[0075] [7] The mounting structure of an electronic component described in any one of [1] to [6], wherein the external electrode has a base electrode layer laminated on the outer surface of the base body, and a Cu layer located on the opposite side of the base electrode layer from the base body and containing Cu as its main component, and the average thickness of the Cu layer is 0.5 μm or more and less than 6 μm. [Explanation of symbols]

[0076] Ta: average thickness Tb: average thickness 20...Base body 22…Plane 22C…side 70A…1st alloy part 70B…Second alloy part 90...Substrate 92...Rand 100...Mounting structure

Claims

1. a substrate having lands; an electronic component having an element body and external electrodes laminated on the outer surface of the element body; a solder containing Sn and Bi; the external electrodes are joined to the lands with the solder, one or more selected from the land and the external electrode contains Ni; At least one selected from the land, the external electrode, and the solder contains Au, and one or more selected from the land, the external electrode, and the solder contain Cu; The solder further includes an alloy portion containing Sn, Cu, Au, and Ni in a region adjacent to the solder. Mounting structure for electronic components.

2. The alloy portion is located in one or more regions selected from the region between the land and the solder and the region between the land and the solder. The electronic component mounting structure according to claim 1 .

3. The alloy portion includes a first alloy portion located in a region between the land and the solder, and a second alloy portion located in a region between the solder and the external electrode. The electronic component mounting structure according to claim 1 .

4. The average thickness of the second alloy portion is greater than the average thickness of the first alloy portion. The electronic component mounting structure according to claim 3 .

5. The external electrodes contain Cu. The electronic component mounting structure according to claim 3 .

6. The element body has a rectangular parallelepiped shape, The external electrodes are arranged on one or more planes selected from one end face and four side faces adjacent to the end face among six planes that form the outer surface of the element body. The electronic component mounting structure according to claim 1 .

7. the external electrode has a base electrode layer laminated on the outer surface of the element body, and a Cu layer located on the opposite side of the element body with respect to the base electrode layer and containing Cu as a main component, The average thickness of the Cu layer is 0.5 μm or more and less than 6 μm. The electronic component mounting structure according to claim 1 .

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