JP2007180401A - Surface-mounting type electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-mounting type electronic component that prevents nonconformities, such as "tombstones" from being generated easily, when mounting the electronic component, prevents making inherent performance that the electronic component has from deteriorating, and is manufactured easily, even if the surface-mounting type electronic component is very compact and light. <P>SOLUTION: A surface-mounting type coil chip component 2 comprises an element body 5, having a core section 4 and a packaging resin section 30; and a pair of edge electrodes 40 formed on both the edge of the element body 5. The external dimensions of the packaging resin section 30 are larger than the maximum external dimensions of flanges 4b, 4c at the core section 4. The edge electrodes 40 are formed each, while covering the outer periphery 30a of both the edges of the packaging resin section 30, and on the outer-periphery surface of each edge electrode 40, a continuous step-like recess 50 is formed in the circumferential direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface-mount type electronic component, and more particularly to a surface-mount type electronic component that is less likely to cause inconveniences such as a tombstone even when it is a small and lightweight surface-mount type electronic component.

  As an example of a surface mount electronic component, for example, a wound electronic component disclosed in Patent Document 1 below is known.

  In this wound electronic component, the outer peripheral surface of the exterior resin portion formed on the outer periphery of the core portion of the ferrite core is polished so as not to protrude from the outer periphery of the end electrode. In paragraph No. 0011 of Patent Document 1, it is described that the outer peripheral surface of the exterior resin portion can be polished to satisfactorily adsorb electronic components and improve the stability on the substrate.

  However, in the conventional surface mount electronic components such as the wound electronic component shown in Patent Document 1, the tombstone phenomenon at the time of mounting the components on the board has become a problem along with the reduction in size and weight. . The tombstone phenomenon means that when mounting a surface-mounted electronic component on a substrate, the electronic component starts up due to an imbalance of moments generated on the solder paste surfaces of the end electrodes formed at both ends of the electronic component. This is a phenomenon that results in poor bonding. There is also a phenomenon called shifting, in which a component shift occurs in the lateral direction and floats from the land.

  3 and 4 and paragraph number 0015 of Patent Document 1 disclose that the bonding strength of the solder is improved by forming a groove in the end electrode. However, the grooves shown in FIGS. 3 and 4 of Patent Document 1 are grooves formed in the axial direction of the ferrite core, and it was difficult to prevent the tombstone phenomenon.

This is because the axial groove shown in Patent Document 1 has a small amount of solder that wraps around the lower surface of the end electrode. Although it may be possible to eliminate the tombstone phenomenon by making the axial grooves relatively large or increasing the number, the volume of the ferrite core is reduced and the performance as a coil component is reduced. Moreover, manufacturing a groove or the like on the ferrite core complicates the manufacturing process.
JP 10-163033 A

  The present invention has been made in view of such a situation, and the object of the present invention is to prevent inconvenience such as a tombstone at the time of mounting even if it is a small and lightweight surface-mount type electronic component. It is an object of the present invention to provide a surface-mount type electronic component that is easy to manufacture without degrading the performance.

In order to achieve the above object, a surface mount electronic component according to the present invention is
An element body having a core portion and an exterior resin portion;
A surface mount electronic component having a pair of end electrodes formed at both ends of the element body,
The outer dimension of the outer resin part is larger than the maximum outer dimension of the core part,
The end electrodes are formed so as to cover the outer periphery of both ends of the exterior resin part,
A stepped recess that is continuous in the circumferential direction is formed on the outer peripheral surface of each end electrode.

  In the surface-mount type electronic component according to the present invention, even when the surface-mount type electronic component is particularly small and light, when the solder is reflowed at the time of mounting, it is applied to the bottom surface of the end electrode formed at both ends of the electronic component. Solder enters the formed step-shaped recess. Since the step-like recesses are formed continuously in the circumferential direction of the end electrodes, a sufficient amount of solder can be secured. As a result, the so-called tombstone phenomenon can be effectively prevented and mounting defects can be prevented.

  Moreover, in this invention, the step-shaped recessed part is formed by forming an edge part electrode so that the outer periphery of both ends of the exterior resin part which has an outer dimension larger than the largest outer dimension of a core part may be covered. For this reason, it is not necessary to process the core part itself, the volume of the core part is not reduced, and the performance as an electronic component is not affected at all. In addition, since the stepped recess can be formed by resin molding, the manufacturing process is not complicated.

  Preferably, the stepped recess is formed with a predetermined width (W1) inward from the end face of each end electrode, and the ratio (W1 / W0) to the total width (W0) of each end electrode is 0. .1 to 0.8. When this ratio is too small, the effect of the present invention is small. On the other hand, if the ratio is too large, the area of the end electrode that directly contacts the substrate is reduced when the electronic component is mounted on the substrate.

  Preferably, the stepped recess is formed such that the depth (H1) from the maximum outer peripheral surface of each end electrode is 10 to 40 μm. When this depth is too small, the effect of this invention is small. On the other hand, if the depth is too deep, the maximum outer dimension of the core portion is relatively small with a limited chip size, and the electrical performance tends to deteriorate.

  Preferably, the ratio (H1 / H0) of the depth (H1) of the stepped recess to the total height (H0) of the maximum outer peripheral surface of the end electrode is in the range of 0.011 to 0.045. When this ratio is too small, the effect of the present invention is small. On the other hand, if this ratio is too large, the maximum outer dimension of the core portion becomes relatively small with a limited chip size, and the electrical performance tends to deteriorate.

Preferably, the core part is a ferrite core having flanges at both ends of the core part,
A coil is wound around the core portion of the ferrite core,
The exterior resin portion covers the periphery of the core portion around which the coil is wound.

Preferably, the exterior resin portion has a flange covering portion that covers a part of the flange of the ferrite core,
The end electrode is formed so as to directly cover the outer peripheral surface of the flange from the end surface of the flange and to cover the flange covering portion of the exterior resin portion.

  When the surface mount type electronic component is a coil chip component, an exterior resin part is often formed around the coil, and when the exterior resin part is manufactured, the shape of the exterior resin part is devised. A step-like recess that is continuous in the circumferential direction can be easily formed on the outer periphery of the partial electrode.

  However, the present invention can be applied not only to the coil chip component but also to a surface mount electronic component in which, for example, the core portion has a laminated structure of an internal electrode layer and an insulating layer.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a longitudinal sectional view of a coil chip component as a surface mount electronic component according to an embodiment of the present invention.
2 is a cross-sectional view of a main part of a mold showing an example of a manufacturing process of the coil chip component shown in FIG.
3 is a cross-sectional view of the main part of the coil chip component shown in FIG.

  As shown in FIG. 1, a coil chip component 2 as a surface mount electronic component according to an embodiment of the present invention has a drum core 4 as a core portion (core material). The drum core 4 is made of a ferrite material. The drum core 4 has a core part 4 a in which a wire 10 a constituting the coil part 10 is wound along the axial direction of the core 4.

  A first flange 4b and a second flange 4c are integrally formed at the first end and the second end, which are both ends in the axial direction of the core 4a. The outer dimensions of the first flange 4b and the second flange 4c are larger than the outer diameter of the core 4a.

  The cross section of the core part 4a is not particularly limited, and may be a rectangular cross section, a circular cross section, or other cross sectional shapes. The cross-sectional shapes of the first flange 4b and the second flange 4c are not particularly limited, and may be a rectangular cross-section, a circular cross-section, or other cross-sectional shapes. The first flange 4b and the second flange 4c have the same size. For example, in the case of a rectangular cross section, the length is about 0.82 mm and the width is about 0.3 mm. Moreover, the outer diameter of the core part 4a is about 0.42 mm, and the axial direction full length of the drum core 4 is about 1.61 mm.

  As shown in FIG. 1, the connecting portions 10b and 10c formed at both ends of the wire 10a constituting the coil portion 10 are connected to the base electrode layer 20 at the outer peripheral positions of the flanges 4b and 4c. The connecting portions 10b and 10c of the wire 10a are fixed to the outer circumferences of the flanges 4b and 4c by means such as thermocompression bonding after the base electrode layer 20 is formed, and these connecting connections are ensured. Alternatively, the connecting portions 10b and 10c of the wire 10a are subjected to thermocompression bonding before the base electrode layer 20 is formed on the outer circumferences and end faces of the flanges 4b and 4c, and then the base electrode layer 20 is formed. May be connected.

  The base electrode layer 20 is an electroless Ni plating with a first layer of 1.0 to 2.0 μm and a second layer of Ni electroplating with a thickness of 1.0 to 2.0 μm.

  After the base electrode layer 20 and the connecting portions 10b and 10c are connected, the outer resin portion 30 is formed by molding a resin in the outer circumferential concave portion of the core portion 4a where the coil portion 10 is formed. It does not specifically limit as resin which comprises the exterior resin part 30, An epoxy resin, a phenol resin, a diallyl phthalate resin, a polyester resin etc. are illustrated.

  The exterior resin part 30 is molded using, for example, molds 80 and 82 shown in FIG. As shown in FIG. 2, the connected drum core 4 in which the coil portion 10 is formed inside the plurality of cavities 84 formed by closing the molds 80 and 82 is connected to the first drum core 4 of the adjacent drum core 4. The flange 4b is arranged side by side in the axial direction so as to contact the end face of the second flange of the adjacent drum core 4.

  The molds 80 and 82 are formed with holding convex portions 86 for holding the outer periphery of the contact portion between the first flange 4b and the second flange 4c of the drum core 4 disposed adjacent to each other. A circumferential gap 88 for forming the resin flange covering portion 30a shown in FIG. The circumferential gap 88 communicates with the cavity 84, and resin is injected into the cavity 84 and molded, and the molds 80 and 82 are opened, so that the exterior resin part 30 having the flange covering part 30a shown in FIG. A plurality of integrated element bodies 5 are obtained.

  The outer diameter of the exterior resin portion 30 of each element body 5 is larger than the outer dimensions (the maximum outer dimensions of the core portion) of the first flange 4b and the second flange 4c, and the first flange 4b and the second flange 4c. A flange covering portion 30a having a predetermined thickness is formed on the outer periphery. The flange covering portion 30a is molded integrally with the exterior resin portion 30, and is formed so as to cover the outer periphery of the flange portions 4b and 4c from the inner side to the outer side to the middle position in the axial direction.

  The thickness of the flange covering portion 30a corresponds to the depth H1 of the step-shaped recess 50 described later. Further, the axial length of the flange covering portion 30a is determined so as to appropriately adjust the axial width (W1) of the step-shaped recess 50 described later.

  After the exterior resin portion 30 is formed, the coil chip component 2 is obtained by forming a pair of end electrodes 40 at both axial ends of the element body 5. Since the end electrode 40 is formed after the exterior resin portion 30 is formed, it cannot be formed by the electrode paste film baking process.

  In this embodiment, each end electrode 40 has electroless Ni plating of 1.0 to 2.0 μm for the first layer, electrolytic Ni plating of 1.0 to 2.0 μm for the second layer, and 3 for the third layer. Electrolytic Sn plating of 0.0 to 4.0 μm.

  Each end electrode 40 is formed so as to directly cover the outer peripheral surface of the flange 4b, 4c from the end face of each flange 4b, 4c, and to cover the flange covering portion 30a of the exterior resin portion 30. Each end electrode 40 is directly connected to the base electrode layer 20 and the connecting portions 10b and 10c at the end surfaces of the flanges 4b and 4c and a part of the outer peripheral surface of the flanges 4b and 4c. Moreover, since each end electrode 40 is formed so as to cover the flange covering portion 30a of the exterior resin portion 30, a step-like recess 50 that is continuous in the circumferential direction is formed on the outer peripheral surface of each end portion 40. Is done.

  As shown in FIG. 1, the step-shaped recess 50 is formed with a predetermined width (W1) from the axial end surface of the element body 5, and the ratio (W1 / W0) to the total width (W0) of each end electrode. ) Is 0.1 to 0.8. If this ratio is too small, the effect of suppressing the tombstone phenomenon tends to be small. If the ratio is too large, as shown in FIGS. 1 and 3, when the coil chip component 2 is mounted on the substrate 60, the area of the end electrode 40 that directly contacts the substrate 60 becomes small. .

  Further, the stepped recess 50 is formed such that the depth (H1) from the maximum outer peripheral surface dimension of each end electrode 40 is 10 to 40 μm. If the depth H1 is too small, the effect of suppressing the tombstone phenomenon tends to be small. On the other hand, if the depth H1 is too deep, the maximum outer dimensions of the flange portions 4b and 4c in the drum core 4 are relatively small with a limited chip size, and the electrical performance tends to deteriorate. .

  The ratio (H1 / H0) of the depth (H1) of the stepped recess 50 to the total height (H0) of the maximum outer peripheral surface of each end electrode 40 is in the range of 0.011 to 0.045. If this ratio is too small, the effect of suppressing the tombstone phenomenon tends to be small. On the other hand, if the ratio is too large, the maximum outer dimensions of the flange portions 4b and 4c in the drum core 4 are relatively small with a limited chip size, and the electrical performance tends to deteriorate.

  In the present embodiment, in particular, even when the chip maximum height H0 is 0.9 mm or less and the coil tip part 2 is 5 mg or less in light weight, during solder reflow during mounting, as shown in FIG. Further, the solder 70 enters the stepped recess 50 formed on the bottom surface of the end electrode 40. Since the step-shaped recess 50 is formed continuously in the circumferential direction of the end electrode 40, the amount of wraparound of the solder 70 can be sufficiently secured. As a result, the so-called tombstone phenomenon can be effectively prevented and mounting defects can be prevented. For example, in the conventional coil chip component (there is no stepped recess 50), the tombstone phenomenon occurred at a ratio of about 10 per 100,000, whereas the embodiment of the present invention (the stepped recess 50) In some cases, no tombstone phenomenon occurred.

  In the present embodiment, the stepped recess 50 is formed by forming the end electrode 40 so as to cover the outer periphery of both ends of the exterior resin part 30 having an outer dimension larger than the maximum outer dimension of the flanges 4b and 4c. It is formed. For this reason, it is not necessary to process the flange itself, the volume of the flange does not decrease, and the performance as a coil chip is not affected at all. In addition, since the stepped recess 50 can be formed by resin molding, the manufacturing process is not complicated.

The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.
For example, the specific cross-sectional structure of the coil chip component according to the present invention is not limited to the embodiment shown in FIG. 1 and may have various aspects. In addition, the present invention can be applied not only to the coil chip component 2 but also to a surface mount type electronic component in which the core portion has a laminated structure of an internal electrode layer and an insulating layer, for example.

FIG. 1 is a longitudinal sectional view of a coil chip component as a surface mount electronic component according to an embodiment of the present invention. 2 is a cross-sectional view of the main part of the mold showing an example of the manufacturing process of the coil chip component shown in FIG. 3 is a cross-sectional view of the main part of the coil chip component shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Coil chip component 4 ... Drum core 4a ... Core part 4b ... 1st flange 4c ... 2nd flange 5 ... Element main body 10 ... Coil part 10a ... Wire 10b, 10c ... Connection part 20 ... Underlayer electrode layer 30 ... Exterior resin Part 30a ... Flange coating part 40 ... End electrode 50 ... Stepped concave part 60 ... Substrate 70 ... Solder 80, 82 ... Mold 84 ... Cavity 86 ... Holding convex part 88 ... Circumferential clearance

Claims (7)

An element body having a core portion and an exterior resin portion;
A surface mount electronic component having a pair of end electrodes formed at both ends of the element body,
The outer dimension of the outer resin part is larger than the maximum outer dimension of the core part,
The end electrodes are formed so as to cover the outer periphery of both ends of the exterior resin part,
A surface-mount type electronic component in which a stepped concave portion continuous in the circumferential direction is formed on the outer peripheral surface of each end electrode.   The stepped recesses are formed with a predetermined width (W1) inward from the end face of each end electrode, and the ratio (W1 / W0) to the total width (W0) of each end electrode is 0.1 to 0.1. The surface mount electronic component according to claim 1, wherein the surface mount electronic component is 0.8.   3. The surface-mount type electronic component according to claim 1, wherein the stepped recess is formed such that a depth (H1) from the maximum outer peripheral surface of each end electrode is 10 to 40 μm.   The ratio (H1 / H0) of the depth (H1) of the stepped recess to the total height (H0) of the maximum outer peripheral surface of the end electrode is in the range of 0.011 to 0.045. The surface mount electronic component as described. The core part is a ferrite core having flanges at both ends of the core part,
A coil is wound around the core portion of the ferrite core,
The surface-mount type electronic component according to any one of claims 1 to 4, wherein the exterior resin portion covers a periphery of a core portion around which the coil is wound. The exterior resin portion has a flange covering portion that covers a part of the flange of the ferrite core,
The surface according to any one of claims 1 to 5, wherein the end electrode is formed so as to directly cover an outer peripheral surface of the flange from an end surface of the flange and to cover a flange covering portion of the exterior resin portion. Mounted electronic components.   The surface-mount type electronic component according to claim 1, wherein the core portion has a laminated structure of an internal electrode layer and an insulating layer.

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