JP2000049019A - Coil device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve an environmental problem by using a conductive adhesive for the connection of lead terminals to the main body of a coil, and at the same time, to improve the strength of adhesion of the adhesive with respect to that of soldering by eliminating the weak point, that is, the low adhesive strength of the conventional adhesive. SOLUTION: A coil device has a main body 1 of a coil constituted by winding a winding 5 around a cylindrical magnetic core 2 and platy lead terminals 11, which are firmly stuck to both end faces of the core 2 with a conductive adhesive 20 together with the terminals 6 of the winding 5. Each lead terminal 11 is buried closer to a base part 12 than the adhesive 20. The front end side connection 13 of each terminal 11 is formed into a narrow width and a small wall thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil device used for a chip inductor or the like, and is particularly suitable for a small-sized surface mounting coil device.

[0002]

2. Description of the Related Art Conventionally, as a small coil device, for example, as shown in JP-A-64-46907, a winding is applied to a center portion of a drum core, and a conductive layer on an end face of both ends of a core is wound together with a winding terminal. A configuration for soldering lead terminals has been known.

[0003] Further, there is a type in which a coil body is attached to a lead frame in which plate terminals are continuously pressed, soldered, and then resin-molded.

[0004]

In a conventional coil device using a lead terminal, a connection portion of the lead terminal must be soldered to a winding terminal of the coil body and a core conductive layer. Therefore, it was necessary to form a conductive layer on the end face of the core in advance. In addition, since lead terminals are processed one by one and taped in advance to establish a continuous production system, there is a problem that the number of man-hours increases.
Furthermore, when used as a surface mount type component (SMD component), reflow soldering is required, and thus an external mold is required. However, since the dimensions of a lead terminal obtained by processing a conductive wire are difficult to obtain, molding was practically impossible.

To cope with these problems, a coil device using a lead frame has been provided. However, a coil device using a lead frame is soldered to a core in order to connect a lead frame terminal and a winding terminal. It is necessary to provide a possible metal part, which has led to an increase in cost.

In view of recent environmental problems, the use of lead-free solder (solder containing no lead) requires selection of a high-temperature winding material and selection of a high-temperature solder, which leads to an increase in cost. Becomes Although it is possible to use a conductive adhesive instead of the conventional soldering, the bonding of small components has a disadvantage that the strength is extremely low.

In view of the above, the present invention solves the environmental problem by using a conductive adhesive for connecting the lead terminals to the coil body, and eliminates the conventional disadvantages of low adhesive strength, It is an object of the present invention to provide a coil device in which the temperature is improved to the level of soldering.

[0008] Other objects and novel features of the present invention will be clarified in embodiments described later.

[0009]

In order to achieve the above object, the present invention is directed to a coil body in which a winding is applied to a columnar core, and a conductive adhesive with both ends of the winding on both end surfaces of the core. A plate-like lead terminal that is adhered and fixed with an agent, wherein the lead terminal is formed such that the width of the leading end side connection portion of the lead terminal embedded in the conductive adhesive is narrower than the mounting base. It is characterized in that it is formed to be thin.

According to a second aspect of the present invention, the thickness of the distal end side connection portion is smaller than the thickness of the mounting base portion and is greater than the thickness of the winding terminal.

According to a third aspect of the present invention, there is provided a coil having a coil main body in which a winding is applied to a columnar core, and a plate-like lead terminal fixed to both end faces of the core together with the winding ends with a conductive adhesive. An apparatus, wherein a pressing plate is stuck to the outside of the distal end side connection portion of the lead terminal with the conductive adhesive,
The winding terminal and the front end side connection portion are sandwiched between the holding plate and the core end surface.

According to a fourth aspect of the present invention, there is provided a configuration in which a resin outer body is provided to cover the coil body including both end surfaces of the core.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a coil device according to the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show the overall structure of a first embodiment of the present invention, and FIGS. 3 and 5 show the arrangement of a lead frame used in the first embodiment and a coil body for the lead frame. .

The coil body 1 has a substantially cylindrical magnetic core 2 (for example, ferrite) with a winding 5 provided thereon. The core 2 is a circular drum core having flanges 3 at both ends.
Is wound between both flanges. The winding ends 6 are drawn out into the depressions 4 on both end faces of the core 2.

The plate-shaped lead terminals 11 constitute surface mounting terminals at portions separated from the lead frame 10 used in the manufacturing process shown in FIGS. 3 to 5, and include a mounting base 12 having a wide portion and a mounting base 12. 12 rising part 1
2a and a distal end side connection portion 13 which is further extended in a narrower width. The bottom surface of the mounting base 12 is a portion to be placed on the mating substrate surface, and a rising portion 12 of the mounting base 12 is provided.
a The upper part which is in contact with the core 2 becomes the core misalignment prevention receiving part 14. In the plate-shaped lead terminal 11, the mounting base 12 of the lead frame 10 is further bent and formed into an inverted L-shape, and the core mounting portions 15 are integrally provided on both sides of the rising portion 12a.

The mounting base 12 and the core mounting portion 15 of the plate-shaped lead terminal 11 have the original thickness of the lead frame 10. The rising portion 12a of the mounting base 12 as shown in FIG.
Has the same thickness, for example, the thickness t of the rising portion 12a.
Is 0.1 mm, and the thickness t 'of the distal end side connecting portion 13 extending to the distal end side is thinner than the rising portion 12a and is equal to or larger than the wire diameter of the winding terminal 6 on the coil body side. For example, if the wire diameter of the winding terminal 6 is 0.06 mm, the thickness t 'of the distal end side connection portion 13 is set to 0.06 mm or set slightly thicker.

The assembly of the coil device using the lead frame 10 is performed in the following procedure.

First, as shown in FIG. 3, a plate-shaped lead terminal 11 having a mounting base 12, a distal end side connection portion 13, and a core mounting portion 15 is formed on a lead frame 10, and the plate-shaped lead terminals 11 opposed to each other are formed. The coil body 1 having the winding 5 provided on the core 2 is disposed therebetween, and the flange 3 of the core 2 is placed on the core placing portion 15 as shown in FIG. Then, the conductive adhesive 20 is applied to the region including the concave portion 4 on both end surfaces of the core 2, that is, the hatched portion X in FIG. The conductive adhesive 20 is obtained by mixing a conductive filler into an epoxy resin or the like, and a commercially available product can be used. By applying the conductive adhesive 20, the winding terminal 6 led out to the concave portion 4 of the core 2 and the distal end side connection portion 13 of the plate-shaped lead terminal 11 become conductive adhesive 2.
0 (becomes buried) in the conductive adhesive 20
The winding terminal 6 is electrically connected to the plate-shaped lead terminal 11 and fixed to the end face of the core 2.

1 and 2 after the conductive adhesive 20 is cured.
The exterior body 30 that covers the periphery of the coil body 1 including both end faces of the core is formed by performing resin molding as described above. The fixing strength of the plate-shaped lead terminal 11 is further improved by forming the exterior body 30. After the molding of the exterior body 30, the lead frame 10 is cut off along the cutting line Y in FIG. 3 to obtain individual parts.

Next, the effects of the above-described plate-shaped lead terminal 11 will be described with reference to FIGS. 6 to 8 and Table 1. FIG.

Assuming a case where the core diameter of the coil body is 1.5 mm, the wire diameter of the winding is 0.06 mm (the thickness of the winding end is 0.06 mm), and the thickness t of the lead frame is 0.1 mm, the actual core is assumed. Because of the tendency of chipping, a 1.5 mm diameter brass rod was used to change the viscosity of the conductive adhesive and the width and thickness of the metal plate corresponding to the tip-side connection of the plate-shaped lead terminals. went. As shown in the front view of FIG. 6A and the plan view of FIG. 6B, the narrow metal plate 41 corresponding to the distal end side connection portion is adhered to the end surface of the brass rod 40 with the conductive adhesive 20. The width W and thickness t 'of the width metal plate 41 and the height H of the peak of the conductive adhesive 20 were measured, and the narrow metal plate 41 was moved in the direction of the arrow P in FIG. The value when peeled off by pulling in the direction (adhesion strength) was measured, and the results in Table 1 below were obtained. The conductive adhesive 20 has a viscosity of 27 Pa · s, 89 Pa
S and 117 Pa · s were used, and a copper flat wire was used as the narrow metal plate 41. FIG. 7 shows the difference in peak height due to the difference in viscosity. FIG. 7 (A) shows the lowest viscosity and the height Ha.
(Average is about 0.15 mm), FIG. (B) shows an intermediate viscosity and height Hb (about 0.25 mm on average), and FIG. (C) shows highest viscosity and height Hc (average) Then it is about 0.4 mm). However, if the thixotropy of the conductive adhesive 20 is high, corners are generated, and the variation becomes large. What affects the bonding strength is the thickness T of the portion covering the narrow metal plate 41 in FIG. This can be inferred from the shape when the metal plate 41 in FIG. 8B is peeled off.

Table 1 Samples Average Value of Adhesive Viscosity H Thickness t 'Width W Adhesive Strength 189 Pa · s 0.21 mm 0.06 mm 0.29 mm 225 gr 2 117 0.44 0.06 0.29 352 3 117 0.1 46 0.07 0.4 304 4 89 0.32 0.06 0.29 186

Since the viscosity of the adhesive of 27 Pa · s is too low, the adhesive strength of the lead terminal of t ′ = 0.06 mm is 10 gr or less, and is excluded from Table 1.

From Table 1 above, when the conductive adhesive is used, the thixotropic property is high, and the thickness of the conductive adhesive covering the narrow metal plate 41 corresponding to the distal end side connection portion of the plate-shaped lead terminal is obtained. Is large enough (that is, the average of the heights H is large), and it is effective to reduce the width and the thickness of the narrow metal plate 41 to improve the adhesive strength.

In the actual coil body 1, the fact that the distal end connecting portion 13 of the plate-shaped lead terminal 11 is narrower and thinner than the wire diameter of the winding terminal 6 is due to the fact that the distal end side connecting portion 13 itself is thin. It is not preferable because the strength becomes insufficient. Therefore, it is desirable that the thickness t ′ of the distal end side connection portion 13 satisfies the following expression: thickness of the winding end ≦ thickness t ′ <thickness t of the mounting base. It can be said that it is desirable that the width W of the distal end side connection portion 13 also satisfies the condition of the thickness of the winding terminal ≦ the width W <the width of the rising portion of the mounting base.

For reference, when the brass bars 40 are surface-bonded to each other as shown in FIG. 9, the bonding strength in the direction of the arrow P is 1.5 mm when the diameter of the brass bar 40 is 1.5 mm regardless of which conductive adhesive is used. 4600 gr or more, which indicates that the experimental results in Table 1 cannot be easily inferred from the conventional surface adhesion measurement results.

According to the first embodiment, the following effects can be obtained.

(1) The plate-shaped lead terminal 11 is attached to the coil body 1.
Can be realized with a sufficiently strong fixing strength even if the structure is bonded with the conductive adhesive 20. Therefore, it is not necessary to form a conductive portion on the surface of the core 2 in advance, and a soldering operation is not required, so that it is possible to reduce man-hours and cost.

(2) A manufacturing process using the lead frame 10 can be adopted, and small and high-precision parts can be obtained. Also,
The resin molding of the exterior body 30 can also be easily performed with high precision, and the exterior body 30 can significantly increase the fixing strength of the plate-shaped lead terminal 11.

(3) The thickness t ′ of the distal end side connection portion 13 is defined as the thickness of the winding terminal ≦ the thickness t ′ <the thickness t of the mounting base, and the width W of the distal end side connection portion 13 is defined as the thickness of the winding terminal. By setting ≦ width W <width of the rising portion of the mounting base, the adhesion of the distal end side connection portion 13 to the coil main body 1 by the conductive adhesive 20 without losing the original strength of the plate-like lead terminal 11 is strengthened. It can be carried out.

(4) The core mounting portion 15 is connected to the plate-like lead terminal 1.
1, the core positioning on the coil body 1 side can be reliably performed, and the movement of the core during resin molding of the exterior body 30 can be prevented.

FIGS. 10 and 11 show a second embodiment of the present invention. In this case, a conductive adhesive 20 is applied as shown in FIG. 11 in a state where the plate-shaped lead terminals 11 are in contact with both end surfaces of the core 2 of the coil body 1, and a metal thin plate 50 is pressed from above. Pasted. In other words, the winding terminal 6 and the distal end side connection portion 13 of the plate-shaped lead terminal 11 are sandwiched between the pressing plate 50 and the end face of the core 2 that substantially match the outer diameter of the core. After the conductive adhesive 20 is cured, the exterior body 30 is molded with a resin. Except that the holding plate 50 is used in combination, it is the same as the above-described first embodiment, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

In the second embodiment, FIG.
As shown in (A), a brass rod 40 having a diameter of 1.5 mm is used (the core is likely to be chipped, so it is used instead in an experiment). An adhesive 20 was applied, and the adhesive strength was measured by pulling in the direction of arrow P in FIG. 12B by changing the viscosity of the conductive adhesive. The adhesive strength is as shown in Table 2 below.

Table 2 Samples Adhesive viscosity Adhesive strength 1 117 Pa · s 294 gr 289 298

The narrow metal plate 41 as the connection portion on the tip end side of the plate-shaped lead terminal was used under the same conditions as the sample 3 in Table 1 described above. In the second embodiment, the narrow metal plate 4
The effect of the width and thickness conditions of 1 on the adhesive strength is smaller than in the first embodiment. From Table 2, it can be seen that despite the small amount of the conductive adhesive 20 used (for pressing and attaching the pressing plate 50), sufficient adhesive strength was obtained. The material of the pressing plate 50 is preferably the same metal material as the material of the lead terminal 11, for example, copper or the like. Further, the shape of the pressing plate 50 can be set to an appropriate area within a range that does not protrude more than the end face of the core.

FIGS. 13A and 13B show a state in which the narrow metal plate 41 and the holding plate 50 are peeled off from the brass bar 40, and the conductive adhesive 20 is peeled over the entire end surface of the brass bar 40. This indicates that the entire end surface of the brass rod 40 contributes to the bonding and realizes a high bonding strength.

According to the second embodiment, the following effects can be obtained.

(1) It is not necessary to use a conductive adhesive having a high viscosity, which easily causes corners.

(2) Even if the amount of the conductive adhesive 20 is small, a high fixing strength of the plate-shaped lead terminal 11 can be obtained.

(3) Since the width L before molding of the exterior body shown in FIG. 14 is stabilized, an improvement in molding yield when the exterior body 30 is molded with resin can be expected. That is, in the first embodiment of FIG. 14A, the width L varies due to the swelling of the conductive adhesive 20 from the end face of the core 2, but in the second embodiment of FIG. Since the height of the conductive adhesive 20 is forcibly pressed by the pressing plate 50, variations in the width dimension L are reduced.

In each of the above embodiments, the drum-shaped magnetic core is exemplified. However, the present invention is not limited to the drum-shaped magnetic core. The present invention is also applicable to a case in which the fixing is performed by using.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0044]

As described above, according to the coil device of the present invention, the use of a conductive adhesive for connection of the plate-shaped lead terminal to the coil main body solves the environmental problem and the conventional bonding method. It is possible to eliminate the disadvantage of low strength and to improve the adhesive strength as much as soldering. In addition, a conductive portion is provided in advance on the end face of the columnar core in order to ensure soldering. However, such processing is not required, and the number of manufacturing steps and cost can be reduced. Furthermore, a lead frame can be employed in the manufacturing process, and resin molding of the exterior body can be performed with high precision and efficiency.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a coil device according to the present invention.

FIG. 2 is a front sectional view of the same.

FIG. 3 is an exploded perspective view when a lead frame is used in a manufacturing process in the first embodiment.

FIG. 4 is a side view showing a distal connection portion of a plate-shaped lead terminal used in the first embodiment.

FIG. 5 is a side view showing an arrangement of a coil main body with respect to a lead frame in the first embodiment.

FIG. 6 is an explanatory diagram showing conditions of an adhesive strength test in the case of the first embodiment.

FIG. 7 is an explanatory diagram showing a change in height of a conductive adhesive caused by a difference in viscosity of the conductive adhesive.

FIG. 8 is an explanatory view showing a state in which a narrow metal plate is bonded by a conductive adhesive and a state in which the metal plate is peeled off.

FIG. 9 is an explanatory view showing a state in which cylindrical brass rods are bonded to each other with a conductive adhesive.

FIG. 10 is a perspective view showing a second embodiment of the present invention.

FIG. 11 is a front sectional view of the same.

FIG. 12 is an explanatory diagram showing conditions of an adhesive strength test in the case of the second embodiment.

FIG. 13 is an explanatory diagram showing a state in which the narrow metal plate and the holding plate adhered by the conductive adhesive are peeled off.

FIG. 14 is an explanatory diagram showing that the degree of variation of a width dimension L differs between the first and second embodiments.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coil main body 2 Substantially cylindrical magnetic core 3 Flange part 4 Indentation part 5 Winding 6 Winding terminal 10 Lead frame 11 Plate-shaped lead terminal 12 Mounting base 13 Front end side connection part 14 Displacement prevention receiving part 15 Core mounting part 20 Conduction Adhesive 30 Outer body 50 Holding plate

Claims (4)

[Claims] A coil body having a columnar core wound thereon;
A coil device having, at both end surfaces of the core, a plate-shaped lead terminal adhered and fixed with a conductive adhesive together with the winding terminal, wherein the lead terminal is embedded in the conductive adhesive rather than a mounting base. A coil device characterized in that the width of the leading end connecting portion of the lead terminal is made narrow and the thickness is made thin. 2. The coil device according to claim 1, wherein a thickness of the distal end side connection portion is smaller than a thickness of the mounting base portion and is equal to or larger than a thickness of the winding terminal. 3. A coil body having a columnar core wound with a coil,
A coil device having, at both end surfaces of the core, a plate-shaped lead terminal adhered and fixed with a conductive adhesive together with the winding terminal, wherein a pressing plate is provided outside the leading end connection portion of the lead terminal. A coil device, wherein the coil terminal is attached with an adhesive so that the winding terminal and the distal end side connection portion are sandwiched between the pressing plate and the core end surface. 4. The coil device according to claim 1, further comprising a resin exterior body covering both ends of the core and covering the coil body.