JP2014229863A - Surface mounting structure of chip component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface mounting structure of a chip component having high reliability even in long term use, in which positional deviation of the chip component is less likely to occur during manufacture.SOLUTION: In a surface mounting structure of a chip component, the land 11 of a wiring board 10 is shaped to have a dent 12 recessed from the land reference plane KL, the electrode 21 of a chip component 20 facing the land 11 is shaped to have a protrusion 22 protruding from the electrode reference plane KD, and in a state where the protrusion 22 is fitted in the dent 12 while superposing partially and holding a solder 30 therebetween, the electrode 21 and the land 11 are connected.

Description

  The present invention relates to a surface mounting structure of a chip component in which an electrode of the chip component is connected to a land of a wiring board by solder.

  For example, Japanese Unexamined Patent Publication No. 11-26910 (Patent Document 1) discloses a surface mounting structure of a chip component in which electrodes of the chip component are connected to lands of a wiring board by solder.

  In general, a wiring board for surface mounting a chip component has a land for bonding an electrode of the chip component made of copper foil or conductive paste formed on the surface of an insulating substrate made of epoxy resin, alumina, or the like. It is provided as a part of a wiring pattern formed by printing. Then, the chip component is mounted on the wiring substrate by bonding the electrode of the chip component to the land with solder.

  The surface mounting of the chip component is easier to manufacture without taking up space than the through-hole mounting in which the lead of the electronic component is fixed to the hole of the printed circuit board or the like, but generally has the following problems. When the chip component is small and light, the chip component floats on the molten solder and easily moves in the solder paste reflow process at the time of manufacture. For this reason, even if the chip component is arranged at a predetermined position on the land before the reflow, the chip component may be displaced after the reflow. Further, when the chip component is large and heavy, the solder layer between the land and the electrode becomes thin. Therefore, since there is a difference in thermal expansion coefficients among the wiring board, solder, and chip parts, there is a possibility that cracks due to thermal fatigue gradually develop in the solder layer when used for a long time.

JP-A-11-26910

  An effective method for solving the latter problem in the surface mounting of the chip component described above is to secure a sufficient thickness of the solder layer and to absorb the shear stress caused by the difference in thermal expansion coefficient by the solder layer. For this reason, in the surface mounting structure of Patent Document 1, an insulator portion protruding from the base material on the electronic component side or the printed board side is provided, and in the insulator portion, the distance between the wiring (land) of the printed board and the electrode of the electronic component is provided. To ensure. However, in this surface mounting structure, a solder layer having a predetermined thickness can be formed, but on the insulator part, the base material on the electronic component side and the base material on the printed board side are in direct contact with each other. For this reason, a large strain is applied to the solder layer during cooling, which may adversely affect the solder life.

  From the above, the present invention is directed to the surface mounting structure of a chip component in which the electrode of the chip component is connected to the land of the wiring board by solder. An object of the present invention is to provide a surface mounting structure of a chip component that is less likely to be displaced during manufacture and that has high reliability even during long-term use.

  The present invention is a surface mounting structure of a chip component in which an electrode formed on the surface of the chip component is connected to a land formed on the surface of the wiring board by solder. In the surface mounting structure of the chip component according to the present invention, when the plane parallel to the base surface of the land and in contact with the upper end of the surface of the land is a land reference plane, the surface of the land is a depression recessed from the land reference plane. It is formed in the shape which has a part. Further, when a plane parallel to the base surface of the electrode facing the land and in contact with the lower end of the surface of the electrode is defined as an electrode reference plane, the surface of the electrode is formed in a shape having a protruding portion protruding from the electrode reference plane. Has been. And it has the structure where an electrode and a land are connected in the state which the said protrusion part overlapped and overlapped with the said hollow part on both sides of solder.

  In a general surface mounting structure of a chip component, both the land of the wiring board and the electrode of the chip component to be joined by solder are planar. In this case, as described above, when the chip component is small and light, the chip component is likely to be misaligned during manufacturing. When the chip component is large and heavy, the solder layer between the land and the electrode can be used for a long time. There is a risk of cracks extending.

  Therefore, in the surface mounting structure of the chip component, the land shape of the wiring board is formed into a shape having a recessed portion recessed from the land reference plane in contact with the upper end. Further, in the electrode of the chip component facing it, the surface shape of the electrode has a protruding portion protruding from the electrode reference plane in contact with the lower end. Then, in the connection portion between the electrode and the land by solder, the electrode and the land are fitted in a state where the protruding portion of the electrode of the chip component partially overlaps the recess portion of the land of the wiring board with the solder interposed therebetween. To be connected.

  By providing the fitting-shaped protruding portion and the recessed portion on the electrode of the chip component and the land of the wiring board, respectively, the movement of the chip component existing in a floating state on the molten solder is restricted during soldering. . Thereby, in the surface mounting structure of the chip component, occurrence of displacement of the chip component can be suppressed.

  Further, at the time of soldering, the molten solder flows toward the indented portion of the land, and the chip component is supported by the molten solder accumulated in the indented portion. For this reason, compared to the case where both the electrode and the land are flat, the flow of molten solder to the periphery of the land is suppressed, and the average thickness of the solder layer finally formed between the electrode and the land Can be thickened. Therefore, it is necessary to secure a sufficient solder layer thickness to absorb the shear stress caused by the difference in thermal expansion coefficient between the wiring board, solder and chip parts, and to suppress the crack extension due to thermal fatigue in the solder layer. Can do. Further, by providing the fitting-shaped protruding portion and the recessed portion, the crack extension path becomes longer as compared with the case where both the electrode and the land are flat. That is, the crack cannot be extended linearly, and becomes a curved path that wraps around between the tip of the projecting portion and the recessed portion that exist in a fitted state. Accordingly, this also extends the solder life. Furthermore, unlike the surface mounting structure described in Patent Document 1, the surface mounting structure of the chip component is not a structure in which the base material on the chip component side and the insulating base on the wiring board side are in direct contact. For this reason, there is no possibility that the solder layer will be greatly distorted during cooling and adversely affect the solder life. As a result, the surface mounting structure of the chip component can ensure high reliability even during long-term use.

  In the surface mounting structure of the chip component, the land reference plane surrounds and touches the recess when viewed from above the wiring board, and the bank portion constituting the upper end is formed to surround the recess. Is preferred.

  When the bank portion does not surround the hollow portion and there is a cut portion in the bank portion, it becomes an outlet for molten solder. On the other hand, when the bank portion is formed so as to surround the hollow portion, the molten solder flows into the hollow portion during soldering, and the outflow to the surroundings is suppressed. For this reason, it becomes possible to strongly support the chip component as compared with the former, and it is possible to increase the average thickness of the solder layer and improve the solder life.

  The surface mounting structure of the chip component is, for example, a structure in which the land reference plane is in contact with the outer periphery of the land and the bank portion constituting the upper end is formed on the outer periphery of the land in a top view of the wiring board. It may be.

  Further, in the surface mounting structure of the chip component, the land reference plane is in contact with the inside of the land in a top view of the wiring board, and at least a part of the bank portion constituting the upper end is formed inside the land. It can also be set as a structure.

  In this case, when the surface of the electrode has a rectangular shape when viewed from the lower side of the wiring board, a part of the bank portion formed inside the land is a long side of the electrode arranged at a predetermined position. It is preferable to be orthogonal to the direction. In addition to the effect obtained by providing the fitting-shaped protrusion and depression described above, this structure is in the long side direction of the electrode where cracks are likely to extend, particularly at both ends where cracks start to extend. In this structure, the thickness of the solder layer is increased. According to this, the probability of occurrence of cracks can be reduced, and the solder life can be further increased.

  In the surface mounting structure of the chip component, for example, when the surface of the electrode has a rectangular shape when viewed from the lower side of the wiring board, it is preferable to adopt the following structure. That is, when the short side direction of the rectangular electrode is the X-axis direction, the long side direction is the Y-axis direction, and the direction orthogonal to the X-axis direction and the Y-axis direction is the Z-axis direction, the protruding portion of the electrode Is an X-Z plane formed in the X-axis direction and the Z-axis direction, and is formed to be plane-symmetric with respect to a plane of symmetry passing through the center of the rectangular electrode. Further, the land recess is also formed so that the land recess is in plane symmetry with respect to the plane of symmetry of the protrusion, facing the protrusion of the electrode disposed at a predetermined position. It becomes the structure which becomes.

  In the rectangular electrode joined with the land by solder, the Y-axis direction, which is the long side direction of the rectangular shape, is a direction in which shear stress due to the difference in thermal expansion coefficients of the wiring board, solder, and chip components increases. , Cracks are easy to extend. Therefore, the protruding portion of the electrode and the recessed portion of the land are formed in plane symmetry so that the plane of symmetry passing through the center is orthogonal to the Y-axis direction with respect to the Y-axis direction in which this crack is likely to extend. As a result, the crack cannot extend linearly in the Y-axis direction, and the extension path of the crack can be a long path that goes around the tip of the protrusion. Therefore, in the Y-axis direction where cracks are likely to extend, the extension of cracks can be suppressed and the solder life can be extended.

  The protruding portion of the electrode of the chip component described above may have a structure in which, for example, the same conductive material as the flat portion between the base surface of the electrode and the electrode reference plane is formed integrally with the flat portion. . Further, at the position where the protruding portion is formed, the main body of the chip component is formed so as to protrude from the base surface of the electrode, and the protruding portion is the same conductive material as the flat portion between the base surface and the electrode reference plane. The structure formed by film-forming simultaneously with a flat part may be sufficient.

  As described above, the surface mounting structure of the chip component described above is a chip component surface mounting structure that is less likely to be misaligned during manufacturing and has high reliability even in long-term use. it can.

It is the figure which showed typically an example of the surface mounting structure of the chip component which concerns on this invention, (a) is the top view which looked at the wiring board 10 and the chip component 20 upwards. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is an enlarged view showing the cross section taken along the alternate long and short dash line BB in (a). It is. FIG. 2A is a diagram illustrating the wiring board 10 of FIG. 1, and FIG. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a). FIG. 2 is a top view of the chip component 20 of FIG. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a). (A)-(c) is a figure which shows the modification of the surface mounting structure of the chip component shown in FIG. 1, respectively. It is a figure which shows another modification, (a) is the top view which looked at the wiring board 10 and the chip component 20d upwards. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is an enlarged view showing the cross section taken along the alternate long and short dash line BB in (a). It is. FIG. 6A is a top view of the chip component 20d shown in FIG. 5. FIG. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a). It is a figure which shows another modification, (a) is the top view which looked at the wiring board 10d and the chip component 20e upwards. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is an enlarged view showing the cross section taken along the alternate long and short dash line BB in (a). It is. FIG. 8A is a top view of the wiring board 10d as viewed from above, showing the wiring board 10d of FIG. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a). FIG. 8A is a top view of the chip component 20e shown in FIG. 7. FIG. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a). It is a figure for demonstrating the formation method of the electrode 11e in the land 11d in the wiring board 10d and the chip component 20e, and is the figure which showed typically a mode that the bank part 13di and the protrusion part 22e were formed in multiple steps. It is the figure which showed typically another example of the surface mounting structure of a chip component, (a) is the top view which looked at the wiring board 10e and the chip component 20f upward. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line CC in (a), and (c) is an enlarged view showing the cross section taken along the alternate long and short dash line DD in (a). It is.

  Generally, a wiring board for surface mounting a chip component is provided with a land for bonding an electrode of the chip component as a part of a wiring pattern made of copper foil or the like formed on the surface of an insulating substrate. . Then, the chip component is mounted on the wiring substrate by bonding the electrode of the chip component to the land with solder.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a surface mounting structure for a chip component according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically showing an example of a surface mounting structure of a chip component according to the present invention. FIG. 1A is a top view of the wiring substrate 10 and the chip component 20 as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is an enlarged view showing the cross section taken along the alternate long and short dash line BB in (a). It is.

  FIG. 2 is a diagram showing the wiring board 10 used in the surface mounting structure of FIG. 1, and FIG. 2A is a top view of the wiring board 10 as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a).

  3 is a diagram showing the chip component 20 used in the surface mounting structure of FIG. 1 upside down. FIG. 3A is a top view of the chip component 20 as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a).

  In addition, in each figure of FIGS. 1-3, each cross section shown with the dashed-dotted line AA and the dashed-dotted line BB respond | corresponds to the same position, as shown with the same code | symbol.

  The surface mounting structure of the chip component shown in FIG. 1 is a structure in which the chip component 20 is surface-mounted on the wiring substrate 10, and the electrodes 21 formed on the surface of the chip component 20 are formed on the surface of the wiring substrate 10. 11 is connected with solder 30. In the wiring substrate 10 shown in FIG. 1, a wiring pattern made of copper foil or the like formed on the surface of an insulating base extends to the left and right in FIG. A land 11 for connecting the chip component 20 is provided as a part of the wiring pattern. Further, as can be seen from FIG. 1C, the chip component 20 shown in FIG. 1 is a chip component having no electrode on the side such as a chip resistor, and a side fillet made of solder cannot be made. Therefore, the land 11 to which the chip component 20 is connected is formed with the same width as the chip component 20 as can be seen from FIGS.

  In the wiring board 10 used in the surface mounting structure of FIG. 1, as shown in FIG. 2, the surface of the land 11 is recessed from the land reference plane KL indicated by a two-dot chain line in (b) and (c). It is formed in a shape having a recess 12. The land reference plane KL here is a plane that is parallel to the base surface SL of the land 11 (the surface of the insulating substrate of the wiring board 10) and is in contact with the upper end UL of the surface of the land 11. The land 11 in FIG. 2 is formed so that the land reference plane KL surrounds and touches the recess 12 and the bank 13 constituting the upper end UL surrounds the recess 12 when viewed from above the wiring board 10. Yes. Further, the land reference plane KL is configured to be in contact with the outer periphery of the land 11, and the bank portion 13 forming the upper end UL is formed on the outer periphery of the land 11. In FIGS. 1B and 1C, the land reference plane KL is indicated by a two-dot chain line.

  Further, as shown in FIG. 3, in the chip component 20 used in the surface mounting structure of FIG. 1, the surface of the electrode 21 facing the land 11 is indicated by a two-dot chain line in (b) and (c). It is formed in a shape having a protruding portion 22 protruding from the electrode reference plane KD. The electrode reference plane KD here is a plane that is parallel to the base surface SD (the surface of the main body of the chip component 20) of the electrode 21 facing the land 11 and is in contact with the lower end DD of the surface of the electrode 21. Further, the protruding portion 22 of the electrode 21 in the chip component 20 is formed integrally with the flat portion 23 by the same conductive material as the flat portion 23 between the base surface SD of the electrode 21 and the electrode reference plane KD. Yes. Note that, also in FIGS. 1B and 1C, the electrode reference plane KD is indicated by a two-dot chain line.

  In the surface mounting structure of the chip component shown in FIG. 1, the electrodes 21 of the chip component 20 and the lands 11 of the wiring board 10 sandwich the solder layer 31 between them, as shown in FIGS. The protruding portion 22 is connected in a state of being fitted to overlap the recessed portion 12.

  In a general surface mounting structure of a chip component, both the land of the wiring board and the electrode of the chip component to be joined by solder are planar. In this case, as described above, when the chip component is small and light, the chip component is likely to be misaligned during manufacturing. When the chip component is large and heavy, the solder layer between the land and the electrode can be used for a long time. There is a risk of cracks extending.

  Therefore, in the surface mounting structure of the chip component of FIG. 1, in the land 11 of the wiring board 10 shown in FIG. 2, the surface shape of the land 11 is formed to have a recess 12 that is recessed from the land reference plane KL in contact with the upper end UL. ing. Further, the electrode 21 of the chip component 20 facing the electrode 21 has a protruding portion 22 protruding from the electrode reference plane KD in contact with the lower end DD as shown in FIG. Then, at the connection portion between the electrode 21 and the land 11, as shown in FIGS. 1B and 1C, the protruding portion 22 of the electrode 21 is the depression 12 of the land 11 with the solder layer 31 interposed therebetween. And are connected so that they partially overlap each other.

  By providing the fitting-shaped projecting portion 22 and the recessed portion 12 on the electrode 21 of the chip component 20 and the land 11 of the wiring substrate 10, respectively, the chip component that exists in a floating state on the molten solder at the time of soldering. 20 movements are limited. Thereby, in the surface mounting structure of the chip component shown in FIG.

  Further, at the time of soldering, the molten solder flows toward the recessed portion 12 of the land 11, and the chip component 20 is supported by the molten solder accumulated in the recessed portion 12. Therefore, compared to the case where both the electrode and the land are flat, the flow of molten solder to the periphery of the land 11 is suppressed, and the solder layer 31 finally formed between the electrode 21 and the land 11 is suppressed. The average thickness can be increased.

  In particular, in the surface mounting structure of the chip component of FIG. 1, the land reference plane KL surrounds and touches the recessed portion 12 in the upper view of the wiring substrate 10, and the bank portion 13 constituting the upper end UL is connected to the recessed portion 12. It is formed so as to surround it.

  When the bank part does not surround the hollow part and there is a cut part in the bank part, the part becomes an outlet for the molten solder. On the other hand, when the bank portion 13 is formed so as to surround the recess portion 12 as in the land 11 shown in FIGS. 1 and 2, molten solder flows into the recess portion 12 during soldering. Thus, the flow out to the surroundings is suppressed. For this reason, compared with the former, it becomes possible to support the chip component 20 strongly, and it is possible to increase the average thickness of the solder layer 31 and improve the solder life.

  As described above, the thickness of the solder layer 31 sufficient to absorb the shear stress caused by the difference in thermal expansion coefficient among the wiring board 10, the solder 30 and the chip component 20 is ensured, and the heat in the solder layer 31 is ensured. Extension of cracks due to fatigue can be suppressed.

  Further, by providing the fitting-shaped projecting portion 22 and the recessed portion 12, the crack extension path becomes longer than when both the electrode and the land are flat. That is, the crack cannot be extended linearly, and becomes a curved path that goes around between the tip of the protruding portion 22 and the recessed portion 12 existing in a fitted state. Accordingly, this also extends the solder life.

  Further, the surface mounting structure of the chip component in FIG. 1 is not a structure in which the base material on the chip component side and the insulating substrate on the wiring board side are in direct contact with each other, unlike the surface mounting structure described in Patent Document 1. For this reason, there is no possibility that a large strain is applied to the solder layer 31 at the time of cold heat to adversely affect the solder life. Accordingly, the surface mounting structure of the chip component shown in FIG. 1 can ensure high reliability even during long-term use.

  Next, details of the surface mounting structure of the chip component shown in FIGS. 1 to 3 will be described in more detail.

  1, the surface of the electrode 21 of the chip component 20 has a rectangular shape when the wiring substrate 10 is viewed from below. That is, as shown in FIG. 3A, the electrode 21 of the chip component 20 facing the land 11 has a rectangular shape. As shown by the orthogonal coordinate axis on the right side, in FIG. 3, the short-side direction of the rectangular electrode 21 facing the land 11 is the X-axis direction, the long-side direction is the Y-axis direction, and the X-axis direction and the Y-axis direction. The direction orthogonal to each other is taken as the Z-axis direction. In the chip component 20 of FIG. 3, as shown in FIG. 3C, the protruding portion 22 of the electrode 21 is an XZ plane formed in the X-axis direction and the Z-axis direction, and has a rectangular shape. A symmetrical plane (cross section A-A) passing through the center of the electrode 21 is formed in a plane symmetrical triangle. Also in FIG. 1, the orthogonal coordinate axes for the chip component 20 are shown with the Z-axis direction reversed.

  Further, in the surface mounting structure of the chip component of FIG. 1, the recess 12 of the land 11 is also opposed to the protruding portion 22 of the electrode 21 arranged at a predetermined position, as shown in FIGS. As shown in FIG. 4, the depression 12 of the land 11 is formed to have a plane-symmetric triangle shape with respect to the symmetry plane (cross section AA) of the protrusion 22.

  In the surface mounting structure of the chip component shown in FIG. 1, in the rectangular electrode 21 joined to the land 11 by the solder 30, the Y-axis direction that is the long side direction of the rectangular shape is the wiring substrate 10, the solder 30, and the chip component. This is the direction in which the shear stress due to the difference in thermal expansion coefficient of 20 increases, and the direction in which cracks are likely to extend. Accordingly, with respect to the Y-axis direction in which this crack is likely to extend, as shown in FIG. 1C, the projecting portion 22 of the electrode 21 and the recessed portion 12 of the land 11 are made symmetrical planes (cross section AA). ) Are formed so as to be plane-symmetric so as to be orthogonal to the Y-axis direction. As a result, the crack cannot extend linearly in the Y-axis direction, and the extension path of the crack can be a long path that goes around the tip of the protrusion 22. Therefore, in the Y-axis direction where cracks are likely to extend, the extension of cracks can be suppressed and the solder life can be extended.

  4A to 4C are diagrams showing modifications of the surface mounting structure of the chip component shown in FIG. In addition, the BB expanded sectional view of each structure illustrated to FIG.4 (a)-(c) respond | corresponds to the BB expanded sectional view shown in FIG.1 (c), FIG.1 (a). The top view shown in FIG. 4 and the AA cross-sectional view shown in FIG. 1B are the same for the structures shown in FIGS. 4A to 4C.

  In the chip component surface mounting structure shown in FIGS. 4A to 4C, the electrodes 21a to 21c of the chip components 20a to 20c and the lands 11a to 11c of the wiring boards 10a to 10c respectively serve as the solder layers 31a to 31c. Connected with a gap between them. Further, the protruding portions 22a to 22c of the electrodes 21a to 21c are joined in a state of being fitted to each other so as to partially overlap the recessed portions 12a to 12c of the lands 11a to 11c.

  The structure shown in FIG. 1C and the structures shown in FIGS. 4A to 4C are different from each other only in the cross-sectional shapes of the protrusion and the depression. That is, in the structure of FIG. 1C, the protruding portion 22 of the electrode 21 and the recessed portion 12 of the land 11 facing the electrode 21 are formed in a triangular shape in the BB cross section. On the other hand, in the structure of FIG. 4A, the protruding portion 22a of the electrode 21a and the recessed portion 12a of the land 11a facing the electrode 21a are formed in a shape whose surface is an arc in the BB cross section. In the structure of FIG. 4B, the protruding portion 22b of the electrode 21b and the recessed portion 12b of the land 11b opposite to the protruding portion 22b are formed in a trapezoidal shape in the BB cross section. In the structure of FIG. 4C, the protruding portion 22c of the electrode 21c and the recessed portion 12c of the land 11c opposed to the electrode 21c are formed in a rectangular shape on the BB cross section.

  4A to 4C, the protrusions 22a to 22c are recessed with the solder layers 31a to 31c interposed therebetween, in the same manner as the surface mounting structure of the chip component shown in FIG. The parts 12a to 12c are connected in a fitted state. Therefore, at the time of soldering, the movement of the chip components 20a to 20c is restricted, and the occurrence of displacement of the chip components 20a to 20c can be suppressed. Further, the molten solder flows toward the depressions 12a to 12c, and the flow to the periphery is suppressed to increase the average thickness of the finally formed solder layers 31a to 31c, thereby extending cracks due to thermal fatigue. Can be suppressed. Furthermore, the crack extension path becomes longer, and the solder life can be extended.

  FIG. 5 is a view showing another modified example of the surface mounting structure shown in FIG. 1, and FIG. 5A is a top view of the wiring substrate 10 and the chip component 20d as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is an enlarged view showing the cross section taken along the alternate long and short dash line BB in (a). It is.

  6 is a diagram showing the chip component 20d used in the surface mounting structure of FIG. 5 turned upside down. FIG. 6A is a top view of the chip component 20d as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a).

  5 (a)-(c) and FIGS. 6 (a)-(c) correspond to FIGS. 1 (a)-(c) and FIGS. 3 (a)-(c), respectively. Each cross section indicated by the chain line AA and the alternate long and short dash line BB corresponds to the same position as indicated by the same reference numeral.

  In the surface mounting structure of the chip component shown in FIG. 5, the electrode 21d of the chip component 20d and the land 11 of the wiring board 10 are connected with the solder layer 31 interposed therebetween. Further, as shown in FIG. 5C, the protruding portion 22 d of the electrode 21 d is joined in a fitted state in which the protruding portion 22 d partially overlaps the recessed portion 12 of the land 11.

  The structure of FIG. 1 differs from the structure of FIG. 5 only in the internal structure of the chip component 20 and the chip component 20d that are surface-mounted on the wiring board 10. That is, in the chip component 20 used in the structure of FIG. 1, as shown in FIG. 3, the protruding portion 22 is the same conductive material as the flat portion 23 between the base surface SD of the electrode 21 and the electrode reference plane KD. Thus, it was formed integrally with the flat portion 23. On the other hand, in the chip component 20d used in the structure of FIG. 1, as shown in FIGS. 6B and 6C, the main body of the chip component 20d is the base of the electrode 21d at the position where the protrusion is formed. It is formed so as to protrude from the surface SD. The projecting portion 22d is formed of the same conductive material as the flat portion 23d between the base surface SD and the electrode reference plane DD, and is formed by film formation at the same time as the flat portion 23d.

  For example, when the chip components 20 and 20d shown in FIGS. 3 and 6 are chip resistors, a main body generally formed of a thick film on an alumina substrate has a lower specific gravity than a metal electrode. In this case, the chip component 20d having the internal structure of FIG. 6 can be reduced in weight as compared with the chip component 20 having the internal structure of FIG.

  FIG. 7 is a view showing another modified example, and FIG. 7A is a top view of the wiring substrate 10d and the chip component 20e as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is an enlarged view showing the cross section taken along the alternate long and short dash line BB in (a). It is.

  FIG. 8 is a view showing the wiring board 10d used in the surface mounting structure of FIG. 7, and FIG. 8A is a top view of the wiring board 10d as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a).

  FIG. 9 is a view showing the chip component 20e used in the surface mounting structure of FIG. 7 upside down. FIG. 9A is a top view of the chip component 20e as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line AA in (a), and (c) is a diagram showing a cross section taken along the alternate long and short dash line BB in (a).

  FIG. 10 is a diagram for explaining a method of forming the land 11d in the wiring substrate 10d and the electrode 21e in the chip component 20e, and schematically shows a state in which the bank portion 13di and the protruding portion 22e are formed in multiple stages. It is a figure.

  7 to 9 correspond to FIGS. 1 to 3, respectively, and the cross-sections indicated by the one-dot chain line AA and one-dot chain line BB are at the same position as indicated by the same reference numerals. It corresponds.

  In the surface mounting structure of the chip component shown in FIG. 7, the electrode 21e of the chip component 20e and the land 11d of the wiring board 10d are connected with the solder layer 31d interposed therebetween. Moreover, as shown in FIG.7 (c), the protrusion part 22e of the electrode 21e is joined in the fitting state which overlapped with the hollow part 12d of the land 11d partially.

  The above-described surface mounting structure of the chip component is configured such that the land reference plane KL is in contact with the outer periphery of the lands 11 and 11a to 11c when the wiring boards 10 and 10a to 10c are viewed from above. And the bank part which encloses the hollow parts 12 and 12a-12c and comprises upper end UL was formed in the outer periphery of land 11a-11c.

  On the other hand, in the surface mounting structure of the chip component shown in FIGS. 7 to 9, the land reference plane KL is in contact with the inside of the land 11d when the wiring substrate 10d is viewed from above. As can be seen from FIG. 8 and FIG. 7C, a part of the bank 13d that surrounds the recess 12d and forms the upper end UL is formed inside the land 11d. The bank portion 13di is orthogonal to the long side direction (Y-axis direction described above) of the electrode 21e of the chip component 20e disposed at a predetermined position. In addition to the effects obtained by providing the fitting-shaped protrusions and depressions described above, this structure has a long side direction in which cracks easily extend, particularly at both ends where crack extension starts. In this structure, the thickness of the layer 31d is increased. According to this, the probability of occurrence of cracks can be reduced, and the solder life can be further increased.

  In addition, as can be seen from FIG. 7C, a part of the bank portion 13di formed inside the land 11d has a steep slope on the outer side and a gentle slope on the inner side. This is to make it easier for the molten solder to flow into the center of the land 11d during reflow of the solder paste, and to improve the self-alignment of the chip component 20e. Thereby, at the time of soldering, it is possible to suppress the positional deviation of the chip component 20e, and to prevent the protruding portion 22e of the electrode 21e and the bank portion 13di of the land 11d from abutting.

  As shown in FIG. 10, the bank portion 13di of the land 11d in the wiring substrate 10d and the protruding portion 22e of the electrode 21e in the chip component 20e can be formed by the following multistage process. The first method is a method in which the land 11d and the electrode 21e are entirely thickly formed by plating, and then are stepped by etching using a predetermined mask. The second method is a method in which a predetermined mask is used to pile up and form stepwise by plating. In addition, depending on the shape, a method of forming in a batch with a press may be used instead of the multistage process as described above.

  FIG. 11 is a diagram schematically showing another example of the surface mounting structure of the chip component, and FIG. 11A is a top view of the wiring substrate 10e and the chip component 20f as viewed from above. Further, (b) is a diagram showing a cross section taken along the alternate long and short dash line CC in (a), and (c) is an enlarged view showing the cross section taken along the alternate long and short dash line DD in (a). It is.

  A chip component 20f shown in FIG. 11 is a ceramic resonator having three electrodes 21f, which is a chip-type CERALOCK (registered trademark of Murata Manufacturing Co., Ltd.).

  In the surface mounting structure of the chip component shown in FIG. 11, the electrode 21f of the chip component 20f and the land 11e of the wiring board 10e are connected with the solder layer 31e interposed therebetween. Further, as shown in FIG. 11 (c), the protruding portion 22f of the electrode 21f is joined in a fitted state in which the protruding portion 22f partially overlaps the recessed portion 12e of the land 11e.

  The surface mounting structure of the chip component shown in FIG. 11 is also the same as the surface mounting structure of the chip component shown in FIG. 7, and the effect obtained by providing the fitting-shaped protruding portion 22e and the recessed portion 12e described above. In addition, the thickness of the solder layer 31e is increased in the long side direction in which cracks are likely to extend, particularly at both ends where crack extension starts. According to this, the probability of occurrence of cracks can be reduced, and the solder life can be further increased.

  As described above, any of the above-described surface mounting structures of chip components is unlikely to cause misalignment of the chip components during manufacturing, and the chip component surface mounting structure that has high reliability even during long-term use. It has become.

10, 10a to 10e Wiring board 11, 11a to 11e Land KL Land reference plane 12, 12a to 12e Depressed portion 20, 20a to 20f Chip component 21, 21a to 21f Electrode KD Electrode reference plane 22, 22a to 22f Protruding portion 31, 31a-31e Solder layer

Claims (9)

A surface mounting structure of a chip component, in which an electrode formed on the surface of the chip component is connected to a land formed on the surface of the wiring board with solder,
When a plane parallel to the basal plane of the land and in contact with the upper end of the surface of the land is a land reference plane,
The surface of the land is formed in a shape having a hollow portion recessed from the land reference plane,
When a plane parallel to the basal plane of the electrode facing the land and in contact with the lower end of the surface of the electrode is an electrode reference plane,
The surface of the electrode is formed in a shape having a protruding portion protruding from the electrode reference plane,
A surface mounting structure for a chip component, wherein the electrode and the land are connected in a state where the protruding portion partially overlaps the recessed portion with the solder interposed therebetween. In a top view of the wiring board,
The land reference plane surrounds and touches the recess,
2. The surface mounting structure for a chip part according to claim 1, wherein the bank portion constituting the upper end is formed so as to surround the hollow portion. In a top view of the wiring board,
The land reference plane is in contact with the outer periphery of the land,
The surface mounting structure for a chip part according to claim 2, wherein the bank portion constituting the upper end is formed on an outer periphery of the land. In a top view of the wiring board,
The land reference plane is in contact with the inside of the land,
The surface mounting structure for a chip component according to claim 2, wherein at least a part of the bank portion constituting the upper end is formed inside the land. In the lower view of the wiring board,
The surface of the electrode has a rectangular shape,
5. The surface mounting structure for a chip component according to claim 4, wherein a part of the bank portion formed inside the land is orthogonal to a long side direction of the electrode arranged at a predetermined position. In the lower view of the wiring board,
The surface of the electrode has a rectangular shape,
When the short side direction of the rectangular electrode is the X axis direction, the long side direction is the Y axis direction, and the direction perpendicular to the X axis direction and the Y axis direction is the Z axis direction,
The protrusion is
The XZ plane formed in the X-axis direction and the Z-axis direction, the plane being symmetrical with respect to a plane of symmetry passing through the center of the rectangular electrode. The surface mounting structure of the chip component as described in any one of 1 thru | or 5. Opposite the protruding part of the electrode arranged at a predetermined position,
The surface mounting structure for a chip part according to claim 6, wherein the depression of the land is formed so as to be plane symmetric with respect to a plane of symmetry of the protrusion. The protrusion is
8. The chip component according to claim 1, wherein the chip part is formed integrally with the flat part using the same conductive material as the flat part between the base surface and the electrode reference plane. 9. Surface mount structure. In the formation position of the protruding portion, the main body of the chip component is formed so as to protrude from the base surface of the electrode,
The protrusion is
8. The conductive material according to claim 1, wherein the flat portion between the base surface and the electrode reference plane is the same conductive material, and is formed by film formation at the same time as the flat portion. Surface mounting structure of chip parts.

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