JPH05217750A - Chip inductor - Google Patents

Abstract

PURPOSE:To provide a heat-resistant inductor of good quality easy to produce in shorter molding time. CONSTITUTION:A coil 12 is attached to the heads of two T-shaped metallic terminal plates 10 and 11, which are on opposite sides of the coil 12 in such a manner that their heads are opposed. The coil ends 14a and 14b are spot- welded to terminals 10b, 10c, 11b, and 11c on the terminal plates. The coil and the whole or part of the terminal plates, including the terminals, are molded in a package 16. The mold package is made of heat-resistant liquid crystal polymer that contains 30-50% filling agent composed of inorganic filler and/or glass fibers. The liquid crystal polymer is of an I-type thermotropic liquid crystal polyester, which has strong molecular chains of linearly-linked benzene rings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip inductor.

[0002]

2. Description of the Related Art In recent years, various electronic parts have been made into chips in accordance with the miniaturization of electronic devices. Leadless (surface mount type) chip parts require higher reliability than before due to the development of high-density automatic mounting technology, reflow soldering technology, and multifunction of electronic equipment. At the same time, the specifications will vary. An example of a conventional chip inductor is disclosed in Japanese Laid-Open Patent Publication No. 62-5618.

That is, as shown in FIG. 5, a coil element 3 is manufactured by winding a winding 2 on a drum core 1. Then, the metal terminal plate 4 facing the coil element 3
After being mounted so as to straddle the upper surface of the tip of the wire, the coil lead wire 5 which is the end of the winding 2 is soldered to the terminal portion 6 projectingly formed at the tip of the metal terminal plate 4 for electrical and mechanical Connect to.

Further, the coil element 3 and the metal terminal plate 4
A part (including the terminal portion 6) of the above is surrounded by the exterior molded body 7. This exterior molded body 7 is designed to protect from the external environment such as moisture and vibration and to be electrically insulated. The base end side of the metal terminal plate 4 is bent into a substantially U-shape, and the end portion 4a is located outside the bottom portion of the exterior molded body 7 and serves as a mounting surface for a mounting circuit.

[0005]

However, the above-mentioned conventional chip inductor has the following problems. That is, since the exterior molded body 7 is usually made of a thermosetting resin having low heat resistance such as epoxy resin or diallyl phthalate, it takes time at the time of molding (50 to 80).
sec), mass productivity is poor. Therefore, in order to improve mass productivity, it is necessary to manufacture a large number of products in one molding, but in such a case, there is a large variation in the molding pressure of each part in the mold (center part and surrounding parts). Since the filling pressure is not uniform in the part), the final product characteristics also vary.

Further, in the case of an epoxy resin, burrs are generated during molding, so that a post process for removing the burrs is required. Further, since the epoxy resin has a large coefficient of linear expansion, the expansion / contraction of the exterior molded body 7 due to the temperature change during molding or during subsequent use causes peeling of the solder connecting the coil lead wire 5 and the terminal portion 6. , Breakage of the lead wire may occur, resulting in poor connection.

Furthermore, as shown in FIG. 3, since the rate of change of the inductance with respect to the temperature change is large, not only is the design complicated, but it is difficult to use it in a place where the operating temperature environment changes greatly.

The present invention has been made in view of the above background, and an object of the present invention is to provide an inductor which is short in molding time, easy to manufacture, resistant to heat, and good in quality. ..

[0009]

In order to achieve the above-mentioned object, in a chip inductor according to the present invention, a coil element is mounted on the upper surfaces of opposing ends of a pair of metal terminal plates facing each other, and the coil of the coil element is mounted. Connect the lead wire to the terminal portion formed at a predetermined position on the tip side of the metal terminal plate,
A chip inductor formed by surrounding a part of the metal terminal plate including the coil element and at least the terminal portion with an exterior molded body, wherein the exterior molded body is filled with at least one of filler and glass fiber. It is composed of a liquid crystal polymer having a good heat resistance in which a material is mixed.

[0010]

When a predetermined filler is mixed with a liquid crystal polymer having good heat resistance, moldability (filling) is improved without lowering heat resistance (heat distortion temperature). Therefore, it can be filled in the mold in a short time and molded, and the liquid crystal polymer is free from burrs and the like during molding. Since the liquid crystal polymer has a lower coefficient of linear expansion than epoxy resin and the like, the volume variation of the exterior molded body due to temperature change is small. Therefore, even if there is a temperature change, a strong force is not applied to the connecting portion between the coil lead wire and the terminal portion, and the connection is not peeled off.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. As shown in FIG. 1, the tips of the pair of first and second metal terminal plates 10 and 11 are arranged to face each other on a substantially straight line. This first and second metal terminal board 1
The tip ends of 0 and 11 are formed in a substantially T-shape in a plane, and the central portion of the tip is formed with plane arcuate recesses 10a and 11a. And both of these recesses 10a, 11a
Both have opposing surfaces (tips) open, and the arcs of both recesses 10a and 11a have substantially the same radius and the same center point.

Further, the T-shaped ends of both metal terminal plates 10 and 11 serve as first terminal portions 10b and 11b and second terminal portions 10c and 11c, respectively. Further, the base end sides 10d and 11d of both metal terminal plates 10 and 11 are bent in a substantially U-shape.

Then, the coil element 12 is mounted so as to straddle the upper surfaces of the tips of the metal terminal plates 10 and 11 which face each other. Specifically, the coil element 12 is configured by winding a winding wire 14 around a drum core 13 made of ferrite or the like. It is mounted in a stable state by being roughly matched in 11a. Then, as shown in FIG. 2, after mounting, the flange 13 a and both metal terminal plates 10 and 11 (recesses 10 a and 11 a) are bonded and integrated with an adhesive 15.

Further, the coil lead-out wires 14a and 14b on the winding start side and the winding end side of the winding wire 14 respectively have one terminal portion formed on the first and second metal terminal plates 10 and 11, respectively. Then, both are electrically and mechanically connected to the first terminal portions 10b and 11b by welding.

The combination of the terminal portions to be used is arbitrary, and in addition to the above combination, the first metal terminal board 10 can be used.
The first terminal portion 10b, the second terminal portion 11c of the second metal terminal plate 11, and the second terminal portion 1 of the first metal terminal plate 10.
0c and the first terminal portion 11b of the second metal terminal board 11 (characteristically equivalent to the former) and the first metal terminal board 1
0 second terminal portion 10c and second metal terminal plate 11 second
There is a combination of the terminal portions 11c, and a predetermined combination that can adjust the number of turns and obtain a desired inductance is appropriately selected.

The portions of the metal terminal plates 10 and 11 other than the base end sides 10d and 11d and the coil element 12 are also described.
Is surrounded by a rectangular exterior molded body 16. Thus, the chip inductor is formed, and the base ends 10d and 11d exposed to the outside of the exterior molded body 16 serve as the coil terminals of the chip inductor.

Here, in the present invention, the exterior molded body 16 is formed.
Is formed of a liquid crystal polymer having good heat resistance mixed with a filler made of at least one of filler and glass fiber. The liquid crystal polymer has a high heat distortion temperature and must be able to be molded into a three-dimensional shape. Therefore, for example, among thermotropic liquid crystal polyesters, a benzene ring has a rigid molecular chain in a linear chain, What is called an I-type liquid crystal polymer is preferable. This type I liquid crystal polymer has a heat distortion temperature of 250 to 350.
It is ℃ and has the best heat resistance. Since the heat resistance is good as described above, when mounting the manufactured chip inductor on the mounting substrate, it is possible to perform soldering with high-temperature solder which cannot be used conventionally.

Then, a filler made of at least one of an inorganic filler and a glass fiber is blended with the above liquid crystal polymer. The blending amount is about 30 to 50% by weight of the filler. Is preferred. That is, when the amount is less than the range, anisotropy of being strongly oriented in the flow direction is strongly exhibited when filling in the mold during molding, and the filling pressure during molding becomes high. On the other hand, if it is larger than the above range, the heat resistance of the liquid crystal polymer is deteriorated.

As a liquid crystal polymer to be used, as a result of experiments, 280 to 320 are particularly preferable among the above-mentioned type I polymers.
It has been found that it is preferable to set the temperature to ° C. That is, it is considered that when the content exceeds the above range, it becomes difficult to mix a predetermined amount of a filler such as an inorganic filler, resulting in poor fluidity and a high filling thickness. On the contrary, if it is lower than the above range, heat resistance and the like may be affected.
Moldability was sometimes slightly reduced.

Further, as described above, since the predetermined liquid crystal polymer is used in this example, the processing temperature at the time of manufacturing the exterior molded body 16 becomes high. Therefore, in order to prevent the deterioration of each component due to heat during the treatment, in this example, first, the coating film of the winding wire 14 is formed by using polyesterimide or polyamideimide having high heat resistance. .. In addition, the coil element 12 and the first and second metal terminal plates 1
An epoxy adhesive 15 having a high glass transition point (110 ° C. or higher) is used as the adhesive 15 for connection with 0 and 11.

Coil lead wires 14a, 14b and terminal portion 10
The connection with b, 10c, 11b, 11c is performed by welding (spot welding) as described above, but in order to further increase the bonding strength, the terminal portions 10b, 10
c, 11b, 11c, that is, both metal terminal boards 10, 11
Is preferably formed of a copper alloy such as phosphor bronze, and the surface thereof is preferably plated with solder having a tin ratio of 90% or more. With such a configuration, the copper wire forming the winding 14 (coil lead-out wires 14a, 14b) and the terminal portions 10b, 10c, 11b, 11c are fused and integrated. Therefore, after welding, the connection portion is not peeled off.

Furthermore, in order to reduce the characteristics of the obtained chip inductor, that is, the variation in the inductance, the drum core 13 is manufactured from a material having a good pressurizing property (the amount of variation of the inductance with respect to pressurization).

Then, the rate of change of inductance ΔL / with respect to the temperature change of the chip inductor in the above embodiment.
When an example of L is shown, it can be seen that the variation rate is much smaller than that of the conventional one shown by the broken line as shown by the execution line in FIG.

* Experimental results On the metal terminal plates 10 and 11 having the above-mentioned shapes, the winding (47
Turn) 14 is mounted on the drum core 13, and 25% of inorganic filler and 25% of glass fiber are attached around the drum core 13.
Exterior molded body 1 formed by using liquid crystal polymer mixed with 1%
A chip inductor was manufactured by covering with 6 (96 samples). The target value of the inductance at this time is 1
It is 8 μH.

The inductance of the actually manufactured element is 17.640 to 18.38 as shown in FIG.
It was 0 μH, and the average value was 18.053 μH. The errors were + 2.1% and -2.0%. In the case of using the conventional diallyl phthalate, it is about ± 5%. On the other hand, when the mixing amount of the liquid crystal polymer was changed, there was no great difference in the temperature characteristics and the variations in the inductance, and the heat resistance was changed.

In the above embodiment, the metal terminal plate 1
The ends of 0 and 11 are T-shaped, and each has two terminal parts 1
Although the devices provided with 0b, 10c, 11b and 11c have been described, the present invention is not limited to this, and can be applied to chip inductors of various configurations other than those shown in the above-mentioned conventional example.

[0027]

As described above, in the chip inductor according to the present invention, since the exterior molding is made of a predetermined liquid crystal polymer, the molding time (including mold clamping and mold opening time) is 10 seconds. Since it becomes weaker and shorter, mass productivity is dramatically improved. Further, since the molding time is shortened, the number of products manufactured at one time can be reduced, the variation of the molding pressure depending on the place is reduced, and the quality can be stabilized. Furthermore, it is thermally stable and has good heat resistance, and the risk of disconnection between the coil lead wire and the terminal portion is reduced as much as possible.

[Brief description of drawings]

FIG. 1A is a perspective view showing a preferred embodiment of a chip inductor according to the present invention. FIG. 3B is a plan view showing a tip portion of the metal terminal plate.

FIG. 2 is a vertical cross-sectional view of the portion shown in FIG.

FIG. 3 is a graph showing temperature characteristics of the present invention and the conventional chip inductor.

FIG. 4 is a graph showing an example of experimental results.

FIG. 5 is a perspective view showing an example of a conventional chip inductor.

[Explanation of symbols]

 10 1st metal terminal board 11 2nd metal terminal board 12 Coil element 14 Winding wire 14a Winding side coil lead-out wire 14b Winding end side coiling wire lead 16 Exterior molding

Claims (2)

[Claims] 1. A coil element is mounted on the upper surfaces of opposing ends of a pair of metal terminal plates facing each other, and a coil lead wire of the coil element is connected to a terminal portion formed at a predetermined position on the tip side of the metal terminal plate. And a chip inductor formed by surrounding a part of the metal terminal plate including the coil element and at least the terminal portion with an exterior molded body, wherein the exterior molded body is filled with at least one of filler and glass fiber. A chip inductor characterized by being composed of a blended liquid crystal polymer having good heat resistance. 2. The chip inductor according to claim 1, wherein the compounding ratio of the filler is 30 to 50% by weight.