Mounting structure and mounting method for electronic components

Abstract

To provide mounting structure and mounting method of an electronic component that can reliably bring an external electrode into contact with an electrode pad to obtain a good bonding state.SOLUTION: In a mounting structure in which at least two external electrodes 20 of a multilayer ceramic capacitor 10, which is an electronic component, are respectively connected to at least two electrode pads 40 arranged on a substrate 30 at a distance from each other, and a resist film 32 is provided around the electrode pad 40 on the surface of the substrate 30, a predetermined distance is set in the direction of the surface 30a of the substrate 30 between the external electrode 20 disposed on the electrode pad 40 and the resist film 32. A second plating layer 27, which is at least the surface layer of the external electrode 20, contains 99 wt.% or more of Sn.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Conventionally, a mounting structure has been known in which external electrodes of a two-terminal electronic component such as a multilayer ceramic capacitor or an inductor are connected to a pair of electrode pads provided on a substrate having a circuit by a metal joining means typified by soldering (see Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-105969 Summary of the Invention [Problem to be solved by the invention]

[0004] Typically, in this type of mounting structure, a resist film is provided on the surface of the substrate to protect the circuit, and the electrode pads are surrounded by this resist film. The electrode pads are exposed on the surface of the substrate with a predetermined area corresponding to the external electrodes, but depending on the design of the resist film, part of the external electrodes may be placed on the resist film, which may result in the external electrodes not being properly positioned relative to the electrode pads and insufficient soldering.

[0005] Therefore, an object of the present invention is to provide a mounting structure and a mounting method for electronic components that can ensure that the external electrodes are in reliable contact with the electrode pads by making it less likely that the external electrodes will interfere with the resist film, thereby achieving a good bonding state. [Means for solving the problem]

[0006] The mounting structure of an electronic component of the present invention is a mounting structure in which at least two external electrodes of an electronic component are connected to at least two electrode pads arranged spaced apart from each other on a substrate, a resist film is provided around the electrode pads on the surface of the substrate, a predetermined distance is set between the external electrodes arranged on the electrode pads and the resist film in the surface direction of the substrate, and at least the surface layer of the external electrodes contains 99 wt% or more Sn. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a mounting structure and a mounting method for electronic components that can reliably contact the external electrodes with the electrode pads by making it less likely for the external electrodes to interfere with the resist film, thereby achieving a good bonding state. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic perspective view of a multilayer ceramic capacitor according to an embodiment; [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3] FIG. 3 is an enlarged view of part III in FIG. 2. [Figure 4] 1 is a plan view showing a mounting structure of a multilayer ceramic capacitor according to an embodiment. [Figure 5] FIG. 5 is a cross-sectional view of FIG. 4 . [Figure 6] 3 is a flow chart showing an example of a process of a mounting method for a multilayer ceramic capacitor according to an embodiment. [Figure 7] 3 is a plan view illustrating the relationship between the dimensions and arrangement of the external electrodes and electrode pads of the multilayer ceramic capacitor according to the embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment will be described with reference to the drawings. The embodiment relates to a structure and a method for mounting a multilayer ceramic capacitor 10 shown in Figures 1 and 2 on a substrate. First, the multilayer ceramic capacitor 10 will be described.

[0010] Fig. 1 is a schematic perspective view of a multilayer ceramic capacitor 10 according to an embodiment of the present invention, and Fig. 2 is a cross-sectional view taken along line II-II shown in Fig. 1.

[0011] 1, the multilayer ceramic capacitor 10 of the embodiment has a generally rectangular parallelepiped shape as a whole. The multilayer ceramic capacitor 10 includes a laminate 12 and a pair of external electrodes 20 that are spaced apart from each other and disposed on the laminate 12.

[0012] In Fig. 1, arrow T indicates the thickness direction of the multilayer ceramic capacitor 10, the laminate 12, and the external electrodes 20. In Figs. 1 and 2, arrow L indicates the length direction of the multilayer ceramic capacitor 10, the laminate 12, and the external electrodes 20, which is perpendicular to the thickness direction T. In Fig. 1, arrow W indicates the width direction of the multilayer ceramic capacitor 10, the laminate 12, and the external electrodes 20, which is perpendicular to the thickness direction T and the length direction L. The cross-sectional view shown in Fig. 2 shows an LT cross section, which is a cross section along the length direction L and thickness direction T at the center of the width direction W.

[0013] As shown in FIG. 1, the laminate 12 has a pair of main surfaces 17a opposing each other in the thickness direction T, a pair of side surfaces 17b opposing each other in the width direction W, and a pair of end surfaces 17c opposing each other in the length direction L.

[0014] The dimensions of the multilayer ceramic capacitor 10 include, for example, dimensions of 0.2 mm to 1.2 mm in the length direction L, 0.1 mm to 0.7 mm in the width direction W, and 0.1 mm to 0.7 mm in the thickness direction T, but are not limited to these.

[0015] The pair of external electrodes 20 includes a first external electrode 21 arranged at one end of the laminate 12 in the length direction L, and a second external electrode 22 arranged at the other end of the laminate 12 in the length direction L. The first external electrode 21 and the second external electrode 22 each cover an end face 17c of the laminate 12. Hereinafter, when the first external electrode 21 and the second external electrode 22, which have the same configuration, are described without distinction, both may be simply referred to as external electrodes 20.

[0016] As shown in FIG. 2 , the laminate 12 has a plurality of dielectric ceramic layers 13 and a plurality of internal electrode layers 14 alternately stacked along a thickness direction T. The thickness direction T is the stacking direction of the plurality of dielectric ceramic layers 13 and the plurality of internal electrode layers 14. The laminate 12 also has an inner layer portion 12A in which the plurality of internal electrode layers 14 face each other via the dielectric ceramic layer 13, and a pair of outer layer portions 12B consisting only of the dielectric ceramic layers 13 arranged to sandwich the inner layer portion 12A in the thickness direction T. The dielectric ceramic layers 13 include a first dielectric ceramic layer 13a of the inner layer portion 12A and a second dielectric ceramic layer 13b of the outer layer portion 12B. The thickness of the dielectric ceramic layer 13b of the outer layer portion 12B is greater than the thickness of the dielectric ceramic layer 13a of the inner layer portion 12A sandwiched between the internal electrode layers 14.

[0017] The dielectric ceramic layers 13 are formed by firing a ceramic material mainly composed of, for example, barium titanate, and the internal electrode layers 14 are formed of, for example, a metal material typified by Ni, Cu, Ag, Pd, an Ag-Pd alloy, Au, etc., or other conductive materials.

[0018] 2, one of a pair of internal electrode layers 14 adjacent to each other along the thickness direction T with the first dielectric layer 13a sandwiched therebetween is electrically connected to the first external electrode 21, and the other is electrically connected to the second external electrode 22. This results in a structure in which a plurality of capacitor elements are electrically connected in parallel between the first external electrode 21 and the second external electrode 22.

[0019] The thickness of the internal electrode layer 14 is preferably, for example, 0.3 μm or more and 0.4 μm or less. By making the thickness of the internal electrode layer 14 0.3 μm or more, defects such as electrode discontinuities are suppressed. Furthermore, by making the thickness of the internal electrode layer 14 0.4 μm or less, it is possible to suppress a decrease in the proportion of the dielectric layer in the capacitor and a resulting decrease in capacitance.

[0020] The thickness of the first dielectric ceramic layer 13a of the inner layer portion 12A sandwiched between a pair of internal electrode layers 14 is preferably, for example, 0.10 μm or more and 1.00 μm or less. By making the thickness of the first dielectric ceramic layer 13a 0.10 μm or more, deterioration of insulation characteristics can be prevented, leading to improved reliability. On the other hand, making the thickness of the first dielectric ceramic layer 13a 1.00 μm or less promotes thinning of the layer, making it possible to improve capacity. In addition, the number of layers of the first dielectric ceramic layer 13a is preferably, for example, 100 to 900.

[0021] The multilayer ceramic capacitor 10 is manufactured, for example, by laminating materials that will become the dielectric ceramic layers 13 and the internal electrode layers 14 to form a laminate 12, and then firing the materials that will become the laminate 12. Thereafter, external electrodes 20 are formed on both ends of the laminate 12 in the length direction L, thereby manufacturing the multilayer ceramic capacitor 10.

[0022] Fig. 3 shows details of the external electrode 20. Fig. 3 is an enlarged view of the part indicated by III in Fig. 2, and shows the first external electrode 21, but the second external electrode 22 has the same configuration.

[0023] 3, the external electrode 20 of the embodiment includes a base layer 25 that is a sintered metal layer, a first plating layer 26 formed on the base layer 25, and a second plating layer 27 formed on the first plating layer 26. In other words, the external electrode 20 is a conductive laminated film in which a multi-layer plating layer made of the first plating layer 26 and the second plating layer 27 is formed on the base layer 25. However, the external electrode 20 is not limited to this configuration, and for example, the plating layer may be a single layer.

[0024] The underlayer 25 is, for example, a sintered metal layer containing glass in Cu. The glass is a glass component containing oxides such as silica (SiO), alumina (AlO), titanium oxide (TiO), barium oxide (BaO), and zirconia (ZrO). The underlayer 25 can be formed by firing on both ends of the laminate 12 in the longitudinal direction L. The firing of the underlayer 25 may be performed by co-firing, which is performed simultaneously with the firing of the laminate 12, or by post-firing, which is performed separately after the firing of the laminate 12. Note that the metal component of the underlayer 25 may be Ni, Ag, Pd, an Ag-Pd alloy, Au, or the like, in addition to Cu. The underlayer 25 is in direct contact with and electrically connected to the end faces 17c of the laminate 12, which are exposed on both end faces 17c.

[0025] The first plating layer 26 is, for example, a Ni plating layer. The first plating layer 26 is formed on the base layer 25 and covers the base layer 25. The second plating layer 27 is a layer that constitutes the surface layer of the external electrode 20 and is, for example, a Sn plating layer. The second plating layer 27 is formed on the first plating layer 26 and covers the first plating layer 26. The second plating layer 27 is preferably a metal that melts at the reflow temperature during reflow mounting, which will be described later, and preferably contains, for example, Sn. When the second plating layer 27 is a Sn plating layer, the second plating layer 27 preferably contains 99 wt % or more of Sn.

[0026] The external electrode 20 is formed so as to cover the entire end face 17c of the laminate 12 and to straddle four faces, namely, a pair of opposing main faces 17a and a pair of opposing side faces 17b.

[0027] Next, a mounting structure of the multilayer ceramic capacitor 10 according to the embodiment will be described. Fig. 4 is a plan view showing the mounting structure according to the embodiment. Fig. 5 is a VV cross-sectional view of Fig. 4. In the mounting structure according to the embodiment, the multilayer ceramic capacitor 10 is mounted on a substrate 30.

[0028] 4 and 5, the mounting structure according to the embodiment includes a substrate 30, a pair of electrode pads 40 spaced apart from each other on the substrate 30, bonding metals 45 respectively disposed on the electrode pads 40, and a multilayer ceramic capacitor 10. The multilayer ceramic capacitor 10 is mounted on the substrate 30 by the bonding metals 45 formed by reflow mounting.

[0029] The substrate 30 is formed in a sheet shape from an insulating material such as resin, glass, glass epoxy, paper phenol, or ceramics. The surface 30a of the substrate 30 is covered with a resist film 32 made of solder resist, leaving a mounting area 30b. The mounting area 30b is located inside the rectangle indicated by the solid line 30b in FIG. 4. The surface of the mounting area 30b is part of the surface 30a of the substrate 30. The multilayer ceramic capacitor 10 is mounted in the mounting area 30b with its length direction L approximately parallel to the X direction shown in FIGS. 4 and 5 and its width direction W approximately parallel to the Y direction perpendicular to the X direction. The mounting area 30b has a rectangular shape that is long in the X direction.

[0030] The X direction and the Y direction are both planar directions along the surface 30a of the substrate 30. Note that Fig. 4 also shows the length direction L and thickness direction T of the multilayer ceramic capacitor 10 shown in Fig. 1. Fig. 5 also shows the length direction L and width direction W of the multilayer ceramic capacitor 10 shown in Fig. 1. Z in Fig. 5 indicates the up-down direction perpendicular to the X direction and the Y direction.

[0031] The electrode pads 40 include a first electrode pad 41 disposed at one longitudinal end of the mounting area 30b and a second electrode pad 42 disposed at the other longitudinal end. The first electrode pad 41 and the second electrode pad 42 are both rectangular in plan view and have the same dimensions. A separation portion 31 is provided between the first electrode pad 41 and the second electrode pad 42. The separation portion 31 is a part of the surface of the mounting area 30b. The first electrode pad 41 and the second electrode pad 42 are arranged side by side, spaced apart from each other in the X direction, with the separation portion 31 sandwiched between them, so that their positions in the Y direction, which is perpendicular to the X direction, are the same. Hereinafter, when the first electrode pad 41 and the second electrode pad 42, which have the same configuration, are described without distinction, both may be simply referred to as electrode pads 40.

[0032] 4, the electrode pad 40 has two sides along the Y direction and two sides along the X direction. The two sides along the Y direction are a third side 40c that is located on the inner side facing the separation portion 31 and that faces each other, and a first side 40a that is located on the outer side away from the separation portion 31. The two sides along the X direction are a second side 40b and a fourth side 40d that are located apart from each other and face each other in the Y direction.

[0033] 4, the resist film 32 covers the first side 40a, the second side 40b, and the fourth side 40d of the electrode pad 40. That is, both ends of the electrode pad 40 in the Y direction and the outer end in the X direction (the side away from the separating portion 31) are covered with the resist film 32 and are not exposed. The third side 40c of the electrode pad 40 is almost exposed except for both ends in the Y direction that are covered with the resist film 32, and is not covered with the resist film 32. Therefore, the resist film 32 is provided on three sides of the periphery of the electrode pad 40 corresponding to the first side 40a, the second side 40b, and the fourth side 40d.

[0034] The first electrode pad 41 and the second electrode pad 42 are each connected to a wiring (not shown) formed on the surface 30a of the substrate 30. The first electrode pad 41 and the second electrode pad 42 are each provided at an end of the wiring. That is, the wiring is discontinuous with the separation portion 31 sandwiched therebetween, and the multilayer ceramic capacitor 10 is connected to the first electrode pad 41 and the second electrode pad 42, respectively, to establish electrical continuity.

[0035] The first electrode pad 41, the second electrode pad 42, and the wiring are preferably made of a highly conductive metal, and are formed by depositing, for example, Cu on the surface 30a of the substrate 30. The highly conductive metal may also be Ag, Au, or the like.

[0036] In the multilayer ceramic capacitor 10, the first external electrode 21 is connected to the first electrode pad 41 via a bonding metal 45, and the second external electrode 22 is connected to the second electrode pad 42 via the bonding metal 45. Each of the first external electrode 21 and the second external electrode 22 has a rectangular connection surface 20d facing the surface 30a of the substrate 30, which is connected to the bonding metal 45. The connection surface 20d is a surface parallel to the main surface 17a of the laminate 12. The multilayer ceramic capacitor 10 is arranged so that the center in the width direction W coincides with the centers of the first electrode pad and the second electrode pad in the Y direction.

[0037] The multilayer ceramic capacitor 10 thus mounted on the substrate 30 has a length direction L substantially aligned with the X direction, a width direction W substantially aligned with the Y direction, and a thickness direction T substantially aligned with the up-down direction Z perpendicular to the surface 30a of the substrate 30. As a result, one of the pair of main surfaces 17a of the laminate 12 faces the surface 30a of the substrate 30 substantially parallel to the surface 30a.

[0038] The multilayer ceramic capacitor 10 can be mounted on the substrate 30 by reflow. In this embodiment, the multilayer ceramic capacitor 10 is reflow-mounted on the substrate 30 using flux. Flux is commonly used as a soldering accelerator that imparts fluidity to metals used in soldering.

[0039] FIG. 6 is a flow chart showing an example of a method for mounting a multilayer ceramic capacitor 10 by reflow mounting. As shown in FIG. 6, in this mounting method, first, flux is applied to the surface of the electrode pad 40 (step S1). In this case, the flux is composed only of a liquid and does not contain any metal components. Next, the external electrode 20 is placed on the surface of the electrode pad 40 to which the flux has been applied (step S2). Next, the external electrode 20 is reflowed by heating to a predetermined reflow temperature (step S3). The reflow melts the metal of the second plating layer 27 forming the outermost surface of the external electrode 20, and the molten metal mixes with the flux and flows between the connection surface 20d of the external electrode 20 and the surface of the electrode pad 40, thereby spreading. After cooling, the metal mixed in the flux hardens to form a bonding metal 45, which maintains the external electrode 20 and the electrode pad 40 in a connected state. When the second plating layer 27 is a Sn plating layer containing 99 wt% or more of Sn, the metal that becomes the bonding metal 45 by reflow is Sn, but also contains a small amount of Cu that has precipitated from the electrode pad 40. Therefore, the bonding metal 45 contains Sn and Cu, and contains almost no metals other than Sn and Cu. The amount of metals other than Sn and Cu contained in the bonding metal 45 is less than 1 wt%.

[0040] Fig. 7 is a plan view illustrating the relationship between the dimensions and arrangement of the external electrode 20 and the electrode pad 40. Note that the external electrode 20 and the electrode pad 40 in Fig. 7 respectively represent the first external electrode 21 and the first electrode pad 41, but the same is true for the second external electrode 22 and the second electrode pad 42.

[0041] 7, the lengths of the first side 40a and the third side 40c of the electrode pad 40, i.e., the length 40Y of the electrode pad 40 in the Y direction, is longer than the length 20W of the external electrode 20 along the width direction W. The length 40Y of the electrode pad 40 in the Y direction is preferably 110% or more and 115% or less of the length 20W of the external electrode 20 in the width direction W.

[0042] Furthermore, the lengths of the second side 40b and the fourth side 40d of the electrode pad 40, i.e., the length 40X of the electrode pad 40 in the X direction, are longer than the length 20L of the external electrode 20 in the longitudinal direction L. The length 40X of the electrode pad 40 in the X direction is preferably 110% or more and 115% or less of the length 20L of the external electrode 20 in the longitudinal direction L.

[0043] By setting the dimensional ratio of the electrode pad 40 to the external electrode 20 as described above, the connection surface 20d of the external electrode has an area that fits within the area of the electrode pad 40. This makes it less likely that the external electrode 20 will interfere with the resist film 32 around the electrode pad 40, and the entire connection surface 20d of the external electrode 20 is reliably placed on the surface of the electrode pad 40. As a result, mounting using flux can be reliably performed. For example, when the external electrode 20 is automatically mounted using a mounter, depending on the mounting accuracy of the mounter, the external electrode 20 may rest on the resist film 32, resulting in poor bonding; however, in the embodiment, such a problem is less likely to occur.

[0044] Furthermore, it is preferable that a predetermined distance be set between the external electrode 20 arranged on the electrode pad 40 and the resist film 32 in the direction of the surface 30 a of the substrate 30 .

[0045] 7, the separation distance in this embodiment is an X-direction separation distance 50X between an end face 20c of the external electrode 20 and an inner wall surface 32c of the resist film 32 facing the end face 20c. The separation distance also includes a Y-direction separation distance 50Y1 between one side face 20b1 of the external electrode 20 and an inner wall surface 32b1 of the resist film 32 facing the side face 20b1, and a Y-direction separation distance 50Y2 between the other side face 20b2 of the external electrode 20 and an inner wall surface 32b2 of the resist film 32 facing the side face 20b2.

[0046] Each of the X-direction separation distance 50X, the Y-direction separation distance 50Y1, and the Y-direction separation distance 50Y2 is preferably 30.8% or more of the multilayer ceramic capacitor 10. Each of the X-direction separation distance 50X, the Y-direction separation distance 50Y1, and the Y-direction separation distance 50Y2 is preferably 0.004 mm or more. These separation distances may be set according to the size of the multilayer ceramic capacitor 10, but are preferably applied to a "0201" size multilayer ceramic capacitor having a length direction L, width direction W, and thickness direction T of 0.25 mm x 0.125 mm x 0.125 mm, for example.

[0047] By setting the X-direction separation distance 50X, the Y-direction separation distance 50Y1, and the Y-direction separation distance 50Y2 between the external electrode 20 and the resist film 32 in this manner, the entire connecting surface 20d of the external electrode 20 can be reliably placed on the surface of the electrode pad 40 without interfering with the resist film 32 around the electrode pad 40. As a result, mounting using flux can be reliably performed. Furthermore, the inner wall surfaces 32c, 32b1, and 32b2 of the resist film 32 block the flux, preventing it from flowing out unnecessarily, and therefore the metal that becomes the joining metal 45 can be efficiently supplied to the electrode pad 40. Therefore, good mounting can be performed with the minimum amount of flux required.

[0048] The mounting structure according to the embodiment described above is a mounting structure in which at least two external electrodes 20 of a multilayer ceramic capacitor 10, which is an electronic component, are connected to at least two electrode pads 40 arranged spaced apart from each other on a substrate 30, and a resist film 32 is provided around the electrode pads 40 on the surface 30a of the substrate 30. The external electrodes 20 arranged on the electrode pads 40 are spaced apart from each other by predetermined distances in the surface direction of the substrate 30, which are an X-direction separation distance 50X, a Y-direction separation distance 50Y1, and a Y-direction separation distance 50Y2. The second plating layer 27, which is at least the surface layer of the external electrodes 20, contains 99 wt % or more of Sn.

[0049] As a result, when mounting the multilayer ceramic capacitor 10 on the substrate 30, the external electrodes 20 are less likely to interfere with the resist film 32, and the external electrodes 20 can be reliably brought into contact with the electrode pads 40 to obtain a good bond. Because the second plating layer 27, which is the surface layer of the external electrodes 20, contains 99 wt % or more of Sn, the second plating layer 27 melts easily during reflow mounting using flux, allowing for good mounting.

[0050] In the mounting structure according to the embodiment, it is preferable that the X-direction separation distance 50X, the Y-direction separation distance 50Y1, and the Y-direction separation distance 50Y2 are all 30.8% or more of the dimensional tolerance of the multilayer ceramic capacitor 10.

[0051] This makes it possible to ensure a sufficient X-direction separation distance 50X, a sufficient Y-direction separation distance 50Y1, and a sufficient Y-direction separation distance 50Y2, and to more reliably arrange the external electrodes 20 on the electrode pads 40.

[0052] In the mounting structure according to the embodiment, it is preferable that the X-direction separation distance 50X, the Y-direction separation distance 50Y1, and the Y-direction separation distance 50Y2 are all 0.004 mm or more.

[0053] This makes it possible to ensure a sufficient X-direction separation distance 50X, a sufficient Y-direction separation distance 50Y1, and a sufficient Y-direction separation distance 50Y2, and to more reliably arrange the external electrodes 20 on the electrode pads 40.

[0054] In the mounting structure according to the embodiment, the multilayer ceramic capacitor 10 includes, as external electrodes 20, a first external electrode 20 and a second external electrode 22 spaced apart from each other, and each of the first external electrode 21 and the second external electrode 22 has a length direction L along the direction in which they are spaced apart from each other and a width direction W perpendicular to the length direction L, and the electrode pads 40 include a first electrode pad 41 to which the first external electrode 21 is connected and a second electrode pad 42 to which the second external electrode 22 is connected and arranged, and both the first electrode pad 41 and the second electrode pad 42 are substantially rectangular and are arranged in parallel and spaced apart from each other in the length direction L of the external electrodes 20 with a spacer 31 sandwiched therebetween, and the first electrode pads 41 and Each of the first and second electrode pads 42 has a third side 40c that is a side along the width direction W of the outer end portion 20 and is located on the inner side, closer to the separation portion 31, and faces each other; a first side 40a that is located on the outer side, away from the separation portion 31, in the longitudinal direction L of the external electrode 20; and a second side 40b and a fourth side 40d that are sides that are along the longitudinal direction of the external electrode 20 and face each other; and it is preferable that the lengths of the first side 40a and the third side 40c are 110% or more and 115% or less of the length of the external electrode 20 along the width direction W, and that the lengths of the second side 40b and the fourth side 40d are 110% or more and 115% or less of the length of the external electrode 20 along the longitudinal direction L.

[0055] This allows the entire connection surface 20d of the external electrode 20 to be placed reliably on the surface of the electrode pad 40 without interfering with the resist film 32 around the electrode pad 40, ensuring reliable mounting. Furthermore, the resist film 32 blocks the flux and prevents it from flowing out unnecessarily, allowing for good mounting with the minimum amount of flux required.

[0056] In the mounting structure of the embodiment, it is preferable that the resist film 32 is not provided in the spaced portions 31 between the electrode pads 40, and the surface of the substrate 30 is exposed.

[0057] This prevents the laminate 12 of the multilayer ceramic capacitor 10 from being placed on the resist film, which causes the external electrodes 20 to be spaced apart from the electrode pads 40, thereby preventing poor contact, and thus ensuring a good bonding state.

[0058] The mounting method of the embodiment is a mounting method for arranging the external electrodes 20 of the multilayer ceramic capacitor 10 on the electrode pads 40 of the substrate 30, and includes the steps of applying flux to the electrode pads 40, placing the external electrodes 20 on the electrode pads 40 to which the flux has been applied, and reflowing.

[0059] This allows the external electrodes 20 of the multilayer ceramic capacitor 10 to be accurately mounted to the electrode pads 40 of the substrate 30 by reflow mounting.

[0060] The present invention is not limited to the above-described embodiment, and any modifications and improvements that can achieve the object of the present invention are included in the present invention.

[0061] For example, the multilayer ceramic capacitor 10 in the above embodiment is an example of an electronic component, but the electronic component is not limited to this, and other two-terminal electronic components such as thermistors and inductors are also applicable. Furthermore, the electronic component is not limited to a two-terminal electronic component, and may be a three-terminal electronic component, etc.

[0062] The electrode pad 40 is not limited to a rectangular shape, and may have a shape corresponding to the shape of an external electrode of an electronic component, for example. [Explanation of symbols]

[0063] 10 Multilayer ceramic capacitors (electronic components) 20 External electrode 21 First external electrode 22 second external electrode 27 Second plating layer (surface layer) 30 boards 30a Surface of the substrate 31 Separation part 32 Resist film 40 electrode pads 40a First Side 40b Second Side 40c Third Side 40d Fourth Side 41 First electrode pad 42 Second electrode pad 45 Joining metal 50X X direction separation distance (separation distance) 50Y1 Y direction separation distance (separation distance) 50Y2 Y direction separation distance (separation distance)

Claims

1. A mounting structure in which at least two external electrodes of an electronic component are connected to at least two electrode pads arranged spaced apart from each other on a substrate, a resist film is provided around the electrode pad on the surface of the substrate; a predetermined separation distance is set between the external electrode and the resist film when the external electrode is disposed on the electrode pad, the separation distance being in a surface direction of the substrate; the resist film is in contact with a portion of the electrode pad including sides corresponding to the end faces and pair of side faces of the external electrode, and the portion of the electrode pad including the sides corresponding to the end faces and pair of side faces of the external electrode is covered by the resist film and is not exposed, a part of an end surface of the external electrode and a part of an inner wall surface of the resist film face each other; At least the surface layer of the external electrode contains 99 wt % or more of Sn.

2. 2. The electronic component mounting structure according to claim 1, wherein the separation distance is 30.8% or more of the dimensional tolerance of the electronic component.

3. 3. The electronic component mounting structure according to claim 1, wherein the separation distance is 0.004 mm or more.

4. the electronic component includes, as the external electrodes, a first external electrode and a second external electrode spaced apart from each other; the first external electrode and the second external electrode each have a length direction along a direction in which they are spaced apart from each other and a width direction perpendicular to the length direction, the electrode pads include a first electrode pad to which the first external electrode is connected and a second electrode pad to which the second external electrode is connected and the first electrode pad and the second electrode pad are both substantially rectangular and are arranged in parallel and spaced apart from each other in the longitudinal direction with a spacing portion therebetween; Each of the first electrode pad and the second electrode pad is a third side that is along the width direction and is disposed on the inner side of the spaced portion and opposed to each other; and a first side that is disposed on the outer side away from the spaced portion in the length direction. a second side and a fourth side that are along a longitudinal direction of the external electrode and that face each other, the length of the first side and the length of the third side are 110% or more and 115% or less of the length of the external electrode along the width direction, The electronic component mounting structure according to any one of claims 1 to 3, wherein the length of the second side and the length of the fourth side are 110% or more and 115% or less of the length of the external electrode along the longitudinal direction.

5. 5. The electronic component mounting structure according to claim 4, wherein the resist film is not provided in the spaced portion, and the surface of the substrate is exposed.

6. A mounting method for arranging the external electrodes on the electrode pads in the electronic component mounting structure according to any one of claims 1 to 5, comprising: applying flux to the electrode pads; placing the external electrodes on the electrode pads to which the flux has been applied; and a reflow step.

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