JP5369293B2 - Chip inductor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a winding type inductor element having a relatively large inductance value obtained by winding a ferrite core, and more particularly to a chip inductor capable of surface mounting.

Conventionally, a winding type inductor element having a relatively large inductance value obtained by winding a ferrite core is known. These elements were prepared by providing a ferrite core having a cylindrical or prismatic shaft portion and flange portions disposed at both ends thereof, winding a winding around the ferrite core shaft portion, and providing the flange portion on the flange portion. An electrode that can be surface-mounted by fixing both ends of the winding to the electrode (see Patent Document 1). In addition, the winding is wound around the shaft part of the ferrite core, both ends of the winding are fixed to the internal electrode provided in the collar part, the whole is sealed with an exterior resin (mold resin body), and the external connected to the internal electrode There is known an inductor element in which an electrode is extended from a lower side of a side surface of a mold resin body and bent along a bottom surface to be surface-mounted (see Patent Document 2).
JP-A-9-213198 JP 2005-223147 A

  In these inductor elements, the electrode formation on the ferrite core collar is performed by directly bonding the metalized or metal plate electrode to the ferrite core collar with an adhesive, and the internal electrode provided on the ferrite core collar is The end of the winding is fixed by thermocompression bonding or soldering. When the end of the winding is joined to the internal electrode provided on the ferrite core collar by thermocompression bonding, heat of around 450 ° C. is applied. Further, when a lead frame serving as an external electrode is mounted, heat of about 350 ° C. is further applied. The internal electrode provided on the ferrite core collar is bonded with a high heat-resistant epoxy resin due to such a load due to heat application, but there is a problem in that the bonding strength deteriorates due to the heat and is peeled off. It was.

  In addition, for example, when these inductor elements are used in vehicles, they may be exposed to extremely cold to high temperature conditions, and may be exposed to severe vibration / impact conditions. High stability and reliability are required.

  The present invention has been made based on the above-described circumstances, and provides a chip inductor that improves the bonding strength of an internal electrode fixed by an adhesive on the top surface of a ferrite core flange of an inductor element and that can obtain high reliability. The purpose is to do.

The chip inductor of the present invention includes a ferrite core having a shaft portion and flanges disposed at both ends thereof, and a winding wound around the shaft portion and fixed to the internal electrode provided on the upper surface of the flange portion by thermocompression bonding . When a molded resin body sealing the ferrite core and the winding, connected to the internal electrode, and an external electrode composed of the molded resin body or al extending metal plate, the upper surface of the flange portion of the ferrite core Is provided with a concave portion opened toward the shaft portion, and an internal electrode made of a metal plate is fixed to the upper surface of the flange portion with an adhesive. Then, the recess is filled with a part of the adhesive, and the internal electrode made of a metal plate has a thin portion and a thick portion of the adhesive due to the adhesive on the upper surface of the collar and the adhesive in the recess. It is fixed to the buttocks through .

Further, the chip inductor manufacturing method of the present invention provides a ferrite core provided with a shaft portion and a flange portion provided at both ends thereof, and a recess opened toward the direction of the shaft portion on at least one surface of the flange portion, Apply an adhesive on the upper surface of the buttock, fill the recess with an adhesive, and fix an internal electrode made of a metal plate to the buttock through a thin portion and a thick portion of the adhesive. Winding the winding around the shaft part, and thermocompression bonding the end of the winding to the internal electrode fixed to the collar, preparing a lead frame, fixing one end of the lead frame to the upper surface of the internal electrode A frame is arranged above the winding, and the ferrite core, the winding wound around the shaft portion of the ferrite core and a part of the lead frame are sealed in the mold resin body, and the lead frame is started from the upper part of the side surface of the mold resin body. The terminal part of the Dokatto and wherein the bent along the terminal portion extending from the molded resin body on the sides and bottom of the molded resin body.

  According to the chip inductor of the present invention, the concave portion is provided on the upper surface of the ferrite core collar portion to which the internal electrode is bonded by the adhesive, so that the thick portion and the thin portion of the adhesive are provided. Can be provided. As a result, when joining the end of the winding to the internal electrode by thermocompression bonding, the strength deterioration of the adhesive due to heat application is reduced, and the internal electrode retains sufficient bonding strength with respect to the upper surface of the ferrite core collar Is possible. Therefore, high reliability required for in-vehicle use and the like can be obtained.

  Hereinafter, embodiments of the chip inductor according to the present invention will be described with reference to FIGS. In addition, in each figure, the same code | symbol is attached | subjected and demonstrated to the same or equivalent member or element.

  FIG. 1 shows an overall configuration example of a chip inductor according to an embodiment of the present invention. This chip inductor includes a ferrite core 11 having a cylindrical or prismatic shaft portion 11a and flanges 11b and 11b disposed at both ends thereof inside an exterior resin (molded resin body) 25, and a shaft portion 11a. And a winding 12 having both ends fixed to an internal electrode 13 provided on the upper surface of the flange portion 11b. The internal electrode 13 is a copper plate plated with tin or the like, and is fixed to the upper surface of the flange portion 11b with an adhesive, and both ends of the winding 12 are joined by thermocompression bonding.

  One end of a T-shaped copper or other metal plate (external electrode) 21 is fixed to the internal electrode 13, and the other end of the metal plate 21 extends from the upper part of the side surface of the mold resin body 25. The terminal portion 21b is arranged by being bent along the side surface and the bottom surface. The surface of the terminal portion 21b is soldered or tin-plated as necessary to form an electrode terminal portion for surface mounting. Since this electrode terminal part extends to the upper part (above the winding core part) along the side surface of the molded resin body, it plays a role as a spring material / cushion material, and vibration / impact / The stress accompanying expansion and contraction can be absorbed, and the application of stress to the winding core can be reduced.

  The flange portion 11b including the internal electrode 13 of the ferrite core 11, the winding 12 wound around the shaft portion 11a, and a part of the metal plate 21 are covered with a rubber-like resin 23 made of soft silicon resin. The mold resin body 25 is a hard exterior resin made of a thermosetting resin such as an epoxy resin or a thermoplastic resin such as a liquid crystal polymer. The mold resin body 25 seals a part of the T-shaped metal plate 21, and the ferrite core 11. The winding 12 and the entire rubber-like resin 23 covering these are sealed. Therefore, the external electrode terminal portion can be stably held by the hard exterior resin, and the stress accompanying the vibration / impact applied from the outside or the temperature change is provided by providing the winding core portion covered with the soft resin inside. Can be absorbed by a soft resin, and the application of stress to the winding core portion can be reduced.

  FIG. 2A is a top view showing details of the ferrite core, the winding, and the internal electrode, and FIG. 2B is a cross-sectional view taken along the line AA in FIG. FIG. In this inductor element, a concave portion 11c opened toward the shaft portion 11a is provided on the upper surface of the flange portion 11b of the ferrite core 11, and the internal electrode 13 made of a metal plate such as copper is provided on the upper surface of the flange portion 11b. Is fixed by an adhesive 14. The internal electrode 13 includes an arc-shaped cutout portion 13a, and the winding end portion 12a is fixed to the internal electrode 13 by thermocompression bonding with the winding suspended in the cutout portion.

  The concave portion 11c is filled with a part of the adhesive 14, and the upper surface of the flange portion 11b is joined to the internal electrode 13 made of a metal plate by the adhesive 14, so that the internal electrode 13 is thick with the thin surface of the adhesive. It is being fixed to the upper surface of the collar part 11b through the surface. Accordingly, the portion A indicated by hatching in FIG. 3A is a portion having good thermal conductivity due to the thin thickness of the adhesive, and the portion B indicated by hatching in FIG. 3B is the thickness of the adhesive. Since the thickness is thick, it becomes a part with poor thermal conductivity. In this example, the thickness of the thin part of the adhesive is about 10 μm, and the thickness of the thick part of the adhesive (depth of the recess) is about 220 μm. The thickness of the internal electrode is about 0.1 mm.

  According to the results of the peel test (destructive test) of the internal electrodes of the present inventors, heat concentration occurs in the thin part of the adhesive, peeling at the interface between the adhesive and the adherend surface, and the adhesive function is not achieved. ) Has occurred, but the thick part is cohesive failure (peeling in the adhesive). Therefore, by providing the concave portion 11c in the ferrite core flange portion 11b of the internal electrode joint surface, a thick portion and a thin portion of the adhesive 14 are provided, and a place having a good thermal conductivity and a place having a bad heat conductivity are provided. It is possible to reduce the strength deterioration of the adhesive due to heat at the time of joining 12a, and to maintain a sufficient strength even after mounting a metal plate serving as an external electrode.

  Next, a method for manufacturing the chip inductor will be described with reference to FIG. First, as shown to (a), it is open | released toward the direction of the axial part 11a in the cylindrical part or the prismatic axial part 11a, the collar parts 11b and 11b arrange | positioned at the both ends, and at least one surface of the collar part. A ferrite core 11 provided with a concave portion 11c is prepared. The illustrated ferrite core 11 is provided with concave portions 11c and 11c that are open toward the shaft portion 11a on both upper and lower surfaces of the flange portions 11b and 11b. An electrode 13 can be arranged.

  Next, as shown in (b), the internal electrodes 13 are fixed to the upper surfaces of the flange portions 11b and 11b with an adhesive. In this embodiment, the internal electrode 13 is a copper plate plated with tin. The adhesive is made of a highly heat-resistant epoxy resin, filled in the recess 11c, applied to the upper surface of the collar, the internal electrode 13 made of a metal plate is fixed, and the internal electrode 13 is secured by heating and drying. It joins to the upper surface of the part 11b. As a result, the internal electrode 13 made of a metal plate is fixed to the upper surface of the flange portion 11b via the thin surface of the adhesive on the upper surface of the collar portion and the thick surface of the adhesive on the upper surface of the recess.

  Next, the winding 12 is wound around the shaft portion 11a of the ferrite core 11, and the end of the winding is fixed to the internal electrode 13 joined to the upper surface of the flange portion 11b by thermocompression bonding. As shown in (c), the end of the winding is fixed at about 450 ° C. while applying a pressure by the heater chip (heat source) 32 while pulling the end of the winding using a wire pulling jig 31. This is done by applying heat in pulses for about 0.3 seconds. At this time, as shown in (d), since the internal electrode 13 has the arc-shaped cutout portion 13a, the end portion 12a of the winding can be easily positioned so as to pass through the top portion of the arc. Winding can be fixed without any.

  Fixing of the winding end portion by thermocompression bonding is performed by applying a heat of around 450 ° C. As described above, the concave portion 11c of the ferrite core collar portion is filled with a part of the adhesive 14, and from the metal plate Since the internal electrode 13 is fixed to the flange 11b via the thin and thick surfaces of the adhesive, as described above, the strength deterioration of the adhesive due to heat can be reduced.

  Next, as shown in (e), a lead frame (metal plate) 21 to be an external electrode is prepared, and one end of the lead frame (metal plate) 21 is fixed to the upper surface of the internal electrode 13 by soldering or the like. Thus, the lead frame (metal plate) 21 is disposed above the winding 12. At this time as well, heat of about 350 ° C. is applied to the internal electrode 13, but the adhesive 14 that fixes the internal electrode 13 to the flange 11b does not deteriorate. The lead frame (metal plate) 21 includes a rod-shaped portion 21a whose one end is connected to the internal electrode, and a terminal portion 21b that is cross-connected to the other end of the rod-shaped portion 21a. The arc-shaped notch S provided in the vicinity of the T-shaped joint at the center of the terminal portion 21b is for substantially reducing the width of the external electrode to prevent escape of heat during solder joining. It is.

  Next, as shown in (f), the ferrite core 11, the winding 12 wound around the ferrite core, and a part of the lead frame (metal plate) 21 are covered with a rubber-like resin. Then, the portion 23 covered with the rubber-like resin and a part of the lead frame (metal plate) 21 are sealed in the mold resin body 25 by insert molding or the like. In this state, an unsealed terminal portion 21 b of the lead frame (metal plate) 21 extends from the upper part of the side surface of the mold resin body 25. Then, unnecessary portions of the lead frame are lead-cut, and the terminal portion 21b extending from the mold resin body 25 of the metal plate 21 to be the lead terminal is bent along the side surface and the bottom surface of the mold resin body 25, and further solder or By applying tin plating or the like, the inductor element shown in FIG. 1 is completed.

  In the above embodiment, the example in which the winding 12 is formed after the internal electrode 13 is fixed to the ferrite core flange 11b has been described. However, after the winding 12 is formed, the internal electrode 13 is connected to the ferrite core flange 11b. The end 12a of the winding 12 may be fixed to the internal electrode 13.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

It is the perspective view which saw through the inside which shows the example of a whole structure of the chip inductor of one Embodiment of this invention. (A) of the said chip inductor is a top view which shows the part of a ferrite core, a coil | winding, and an internal electrode, (b) is sectional drawing along the AA line of (a) in the collar part of a ferrite core. (A) and (b) are top views of the ferrite core collar vicinity. It is a figure which shows the manufacturing process of the chip inductor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Ferrite core 11a Shaft part 11b Eaves part 11c Recessed part 12 Winding 12a Winding end part 13 Internal electrode 13a Arc-shaped notch 14 Adhesive 21 Metal plate (lead frame)
21a Metal plate rod portion 21b Metal plate terminal portion 23 Rubber-like resin 25 Mold resin body (exterior resin)

Claims (4)

A ferrite core having a shaft portion and flanges disposed at both ends thereof;
Winding wound around the shaft part, both ends fixed to the internal electrode provided on the upper surface of the collar part by thermocompression bonding ,
A molded resin body that seals the ferrite core and the winding;
Wherein connected to the internal electrode, and an external electrode composed of the molded resin body or al extending metal plate,
The upper surface of the flange portion of the ferrite core is provided with a recess opened toward the shaft portion, and the inner electrode made of a metal plate is fixed to the upper surface of the flange portion with an adhesive ,
An internal electrode made of a metal plate is fixed to the flange through a thin portion and a thick portion of the adhesive by the adhesive on the upper surface of the flange and the adhesive in the recess . A chip inductor characterized by that. 2. The chip inductor according to claim 1 , wherein the thickness of the adhesive in the concave portion decreases in the direction of the shaft portion . Prepare a ferrite core provided with a shaft portion, a flange portion disposed at both ends thereof, and a recess opened toward the direction of the shaft portion on at least one surface of the flange portion,
An adhesive is applied to the upper surface of the flange portion, an adhesive is filled in the recess, prior Kitsuba portion, through said reduced thickness portion and a thick portion of the adhesive, the internal electrode made of a metal plate Fixed,
Winding a winding around the shaft portion of the ferrite core, thermocompression bonding the end of the winding to the internal electrode fixed to the flange,
Preparing a lead frame, fixing one end of the lead frame to the upper surface of the internal electrode, and arranging the lead frame above the winding;
The ferrite core, the winding wound around the shaft portion of the ferrite core, and a part of the lead frame are sealed in a mold resin body, and the terminal portion of the lead frame is formed from the upper side surface of the mold resin body. Extension,
A method of manufacturing a chip inductor, wherein the lead frame is lead-cut and a terminal portion extending from the mold resin body is bent along a side surface and a bottom surface of the mold resin body. The method for manufacturing a chip inductor according to claim 3 , wherein the thickness of the adhesive in the concave portion decreases in the direction of the shaft portion .

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