JP2002313629A - Chip type inductor - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To simplify a process, to facilitate manufacture, to set a wide inductance setting range, and to enable packing in a bag. Laser processing is easy and increases yield and reliability. Also, the Q value is increased. SOLUTION: A coil member 14 in which a coil 12 made of a spiral conductive film is formed on an outer circumferential surface of an insulating base 10 in a longitudinal direction.
And external electrodes 16 provided at both ends of the coil member so as to be connected to the ends of the coil, and an insulating layer 18 for protecting the outer periphery of the coil. The insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over its entire length, and the chip thickness / chip width of the chip cross-sectional shape orthogonal to the coil axis is less than 1. The external electrode is formed thicker than the insulating layer on the wide surface of the coil member, and is plated with a material 20 having good solder wettability, including other exposed portions of the conductive film. To increase the Q value, a coil is formed over almost the entire length of the insulating base, and the end face of the chip is made non-conductive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type inductor compatible with surface mounting, and more particularly, to a coil member having a coil formed of a spiral conductive film on an outer circumferential surface of an insulating base in a longitudinal direction. External electrodes provided at both ends of the coil member so as to be connected to the coil ends,
The present invention relates to a chip type inductor having a structure provided with an insulating layer for protecting the outer periphery of a coil. This chip-type inductor is used, for example, in a high-frequency circuit such as a portable device.

[0002]

2. Description of the Related Art Chip type inductors are classified into two types according to the relationship between the direction in which external electrodes are arranged and the direction of the coil axis. The first type is a structure in which the arrangement direction of both external electrodes is orthogonal to the coil axis direction, and the second type is a structure in which the arrangement direction of both external electrodes coincides with the coil axis direction.

In the first type, since the direction in which the magnetic field is generated differs depending on how the chip is placed on the circuit board, it is necessary to attach a marker for confirming the direction on the upper surface of the chip and mount the chip in a prescribed direction based on the marker. there were. For this reason, not only an extra step of forming a marker is required, but also taping packing is required (packing packing is not possible), and a problem arises that packing waste such as paper and plastic is generated every time. On the other hand, in the second type, since the structure has no directionality in principle, the direction in which the magnetic field is generated does not change even when the placement of the chip on the circuit board changes (that is, the electrical characteristics do not change). There are advantages.

A structure in which a coil is formed in the longitudinal direction of a chip so that the arrangement directions of both external electrodes coincide with the coil axis direction has been conventionally realized by a lamination method and a laser processing method.

[0005] In the lamination method, the electric insulating layer and the conductor pattern are alternately laminated and the conductor patterns are sequentially connected to form a coil superimposed in the laminating direction in the electric insulator. In this structure, the lead conductor is connected to an external electrode on the outer surface of the multilayer chip.

In the laser processing method, a conductor film is formed on the entire surface of a bobbin-shaped insulating substrate having a concave central portion, and a groove is helically formed in the concave central portion by laser processing to form a coil. . Here, the cross section perpendicular to the coil axis is square at both ends and the center. The bulging portions at both ends become external electrodes, and the outer periphery of the coil is coated with an insulating resin. Such a chip inductor is disclosed in, for example, Japanese Patent No. 3084482.

[0007]

However, in the case of a chip type inductor using a lamination method, the lamination process is complicated, and the smaller the size, the more the coil must be formed in a small area. Pattern formation becomes difficult. Further, there is also a problem that the bending strength is weak because the conductor part having low strength in the chip cross section takes a considerable area.

On the other hand, a chip type inductor using a laser processing method has few such problems. However, in the conventional structure, since the coil is formed in the recessed central portion, the area where the coil can be formed becomes short, and it is difficult to change the inductance in a wide range. If an attempt is made to produce a high inductance product forcibly, the laser processing interval becomes narrow, and a defective product such as a short circuit is likely to occur, which causes a problem that the yield decreases. In addition, it is necessary to flatten all the surfaces coated with the insulating resin so that any one of the four surfaces of the chip can be adsorbed by the mounting machine, which complicates the process.

Further, in any of the methods, the external electrodes on both end surfaces of the chip block the magnetic field, so that the Q value decreases. In the lamination method, there is a lead conductor.In the conventional laser processing method, the coil end is located in the central concave part and the external electrode is provided on the bulging part outside, so remove the conductor on the chip end face. However, the Q value does not increase.

An object of the present invention is to provide a chip type inductor which can simplify a process, is easy to manufacture, can set a wide range of inductance, and can be packed in a bag without taping. Another object of the present invention is to provide a chip type inductor capable of increasing the Q value. Still another object of the present invention is to provide a chip type inductor which can be easily laser-processed and can increase the yield.

[0011]

According to the present invention, there is provided a coil member having a coil formed of a spiral conductive film on the outer circumferential surface of an insulating base in a longitudinal direction, and both ends of the coil member connected to coil ends. Assuming a structure including an external electrode provided in the portion and an insulating layer for protecting the outer periphery of the coil, the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over its entire length, and is orthogonal to the coil axis. This is a chip-type inductor in which the chip thickness / chip width of the chip cross-sectional shape is less than 1. In the present invention, the rectangular parallelepiped shape means a substantially rectangular parallelepiped shape, and it goes without saying that the shape includes chamfering or rounding of appropriate dimensions.

Further, the present invention provides a coil member having a coil formed of a spiral conductive film on an outer circumferential surface of a longitudinal direction of an insulating base, and an external member provided at both ends of the coil member so as to be connected to the coil end, respectively. Assuming a structure including an electrode and an insulating layer for protecting the outer periphery of the coil, the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over its entire length, and has a chip cross-sectional shape orthogonal to the coil axis. Thickness / chip width is less than 1, and the external electrodes are formed thicker than the insulating layer on both wide surfaces of the coil member, and are plated with a material having good solder wettability, including other exposed portions of the conductive film. Chip type inductors. here,
For example, the first insulating layer covers the outer four sides of the coil member,
The structure may be such that a second insulating layer wider than the width of the coil member and having a flat surface is formed only on the first insulating layers on both of the wide surfaces.

Further, the present invention provides a coil member having a coil formed of a spiral conductive film on an outer circumferential surface of a longitudinal direction of an insulating base, and external members provided at both ends of the coil member so as to be connected to the respective coil ends. Assuming a structure including an electrode and an insulating layer for protecting the outer periphery of the coil, the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over its entire length, and has a chip cross-sectional shape orthogonal to the coil axis. Thickness / chip width is less than 1, the external electrode is formed thicker than the insulating layer only on one wide surface of the coil member, and is plated with a material having good solder wettability, including other exposed portions of the conductive film. A chip inductor that has been treated and the other wide side is a different color than the other side. Here, a non-conductive portion may be formed at both ends of the wide surface facing the external electrode forming surface of the coil member. Further, for example, the first insulating layer covers the four outer peripheral side surfaces of the coil member, and only the first insulating layer on the wide surface facing the external electrode formation surface is wider than the coil member and the surface is wider. A structure in which a second insulating layer which is flat and has a different color from the first insulating layer may be formed.

When the insulating layer has a two-layer structure, the first insulating layer can be made of low-temperature sintered ceramics and the second insulating layer can be made of heat-resistant resin.

When the coil is formed only in the region between the two external electrode forming portions, conductors may be provided on both end surfaces of the coil member.

Further, the present invention provides a coil member having a coil formed of a spiral conductive film on the outer circumferential surface of an insulating base in the longitudinal direction, and an external member provided at both ends of the coil member so as to be connected to the coil end. Assuming a structure including an electrode and an insulating layer that protects the outer periphery of the coil, the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over the entire length thereof, and the coil leaves only near both ends of the insulating base. Thus, a chip-type inductor is formed over substantially the entire length of the insulating base up to the inside of the external electrode, and both end surfaces of the coil member are non-conductive surfaces. Also in this case, it is preferable to set the chip thickness / chip width of the chip cross-sectional shape perpendicular to the coil axis to less than 1.

In the chip-type inductor according to the present invention, the external electrodes can be formed of a cured film of a mixture of, for example, conductive particles and epoxy resin. An exposed portion of the insulating base is provided at a part of the external electrode forming portion near both ends of the coil member, and the external electrode is formed on both the exposed portion of the insulating base and the conductive film to increase adhesion strength. Can be.

[0018]

1 shows an embodiment of a chip type inductor according to the present invention, wherein A is an external perspective view and B is a longitudinal sectional view. A coil member 14 having a coil 12 made of a spiral conductive film formed on an outer circumferential surface of the insulating base 10 in a longitudinal direction; external electrodes 16 provided at both ends of the coil member so as to be connected to coil ends, respectively; 12 is provided with an insulating layer 18 for protecting the outer periphery. The insulating base 10 has a rectangular parallelepiped shape having the same cross-sectional shape over its entire length, and a chip thickness / chip width of a chip cross-sectional shape orthogonal to the coil axis is less than 1 (that is, a horizontally long shape when viewed in the coil axis direction). Is set to The external electrodes 16 are formed thicker than the insulating layer 18 on both wide surfaces of the coil member 14, and are plated with a material 20 having good solder wettability, including other exposed portions of the conductor film.

The insulating substrate 10 is made of, for example, ceramics (eg, alumina) or resin (eg, epoxy resin). A conductor film made of silver, copper, or the like is formed on the entire outer surface by plating or baking of a coating film, and a spiral groove is formed in the conductor film by laser processing to form the coil 12. When a black ceramic is used, good processing can be performed without reflection of laser light. For forming the coil, in addition to such laser processing, groove processing by sandblasting or etching is also possible depending on the dimensions and shape of the coil. As a plating process using a material having good solder wettability, for example, nickel plating is performed first, and then solder plating is performed.

The external electrode 16 is preferably formed of a cured film of a mixture (conductive resin) of conductive particles such as silver or copper and an epoxy resin. This is because the process can be simplified. As a matter of course, a method such as baking of a conductor paste (silver paste or the like) may be used as in the related art. The outer insulating layer 18 is a coil 1
2, a film coated with a resin and cured, or a film obtained by adhering low-melting glass or the like and sintering may be used.

In the present invention, since the chip thickness is smaller than the chip width, the mounting surface can be limited to two wide surfaces (upper and lower surfaces) because of the shape anisotropy.
That is, since the cross section is rectangular and the width of the surface is different (there is anisotropy in the shape), it is easy to align them with either one. For example, as in the above-described embodiment, if the electrical characteristics are satisfied regardless of which one of the wide surfaces is the mounting surface, even if the package is packed in a bag without taping, the parts are fed in a predetermined direction using a parts feeder. It is possible to Further, since the chip thickness is smaller than the chip width, the chip is stabilized without being rolled by force when mounting the chip on the circuit board during mounting, and the chip is unlikely to stand during soldering.
Furthermore, since the surface on which vacuum suction is performed during mounting (the surface opposite to the mounting surface) is limited to two wide surfaces, only the two surfaces need to be finished flat. It is easier than conventional products that must be finished. In the case of an insulating substrate made of alumina ceramic, the dimensional tolerance of the height and width is usually about ± 0.03 mm. Therefore,
In the present invention, the difference between the width and the thickness of the insulating base is 0.06 mm.
Make it bigger. The relationship between the chip width and the chip thickness of the final product is determined in consideration of variations in the thickness of the insulating layer and the external conductor and the possibility of chip alignment due to shape anisotropy. Although it depends on the chip size, in the current 1005 type chip, 0.06 mm <(chip width−chip thickness) ≦ 0.2 mm, more preferably 0.1 mm ≦ (chip width−chip thickness) ≦ 0. It is better to set the range to 2 mm.

FIG. 2 shows another example of the insulating layer. The insulating layer
A thin first insulating layer 22 covers the four outer peripheral sides of the coil member 14 (see A in FIG. 2), and only the first insulating layer on both wide surfaces (upper and lower surfaces) has a width smaller than the width of the coil member. The second insulating layer 24 may be slightly wider and have a flat surface (see FIG. 2B). By doing so, the flatness of the two wide surfaces (upper and lower surfaces) can be further increased, and the vacuum suction at the time of mounting can be performed more stably and reliably. Also, the corners of the coil member 14 are further thinned only with the thin first insulating layer 22,
By providing the second insulating layer 24, corners are sufficiently covered. Such a second insulating layer 24 can be easily formed by transferring a resin coated on a flat member.

When the insulating layer has a two-layer structure, the first insulating layer 22 is made of low-temperature sintered ceramics (a mixture of ceramics and glass) and the second insulating layer
Is preferably made of a heat-resistant resin (epoxy, fluorine, silicon, etc.). When the first insulating layer 22 is made of low-temperature sintered ceramics, a sintering step is required. However, by heating at this time, the corners of the coil 12 which are sharpened by laser processing (the kerf is cut in the conductive film by laser). The corner immediately after formation: see FIG. 3A) can be rounded as shown in FIG. 3B. When the corners of the coil 12 are rounded as described above, there is an advantage that the high-frequency resistance is reduced and the Q value is increased.

As shown in FIG. 4, the coil member 14 has an insulating base 1 on a part of the external electrode forming portion near both ends thereof.
A configuration may be adopted in which a portion 26 where 0 is exposed is provided, and an external electrode is formed on both the exposed insulating substrate portion and the conductive film (the position where the external electrode is formed is indicated by a dotted line). A in FIG.
In FIG. 4B, the portion of the insulating substrate is exposed by removing the conductive film over the entire width of the chip. In FIG. 4B, the portion of the conductive film is removed by exposing the portion of the chip width to expose the portion of the insulating substrate. In the case of only on the conductive film, the adhesion strength of the external electrode may be insufficient, but a part of the external electrode has been roughened by removing a part of the conductive film and exposing the base of the insulating base. Adhesion strength is increased by being configured to be directly adhered to the insulating base.

In the present invention, since the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over the entire length, a coil can be formed using the entire length. Therefore, the same 10 nH
The distribution of the magnetic flux density is determined for the case where the coil is formed over substantially the entire length (A in FIG. 5) and the case where the coil is formed only at the center (the region between the external electrodes) (B in FIG. 5). Was. As can be seen from FIG. 5, the magnetic field exits from the end of the coil, and the distribution of the magnetic flux density is different. It is a well-known matter that the Q value of the coil is increased by not interrupting the magnetic field generated from the coil. However, there is a problem how to prevent the magnetic field from being interrupted.

When a conductor is formed on the end face as in this embodiment, if a coil is formed over substantially the entire length up to the chip end face, the conductor covers a portion where the magnetic field is strong, as shown by a curve a in FIG. The frequency-Q value characteristic is significantly reduced. On the other hand, when the coil is formed only in the central portion, the conductor is less in the portion where the magnetic field is strong, and the decrease in the frequency-Q value characteristic can be suppressed as shown by the curve b in FIG. In consideration of the magnetic flux density distribution shown in FIG. 5, it is better that the coil end is far from the chip end face, and it is preferable that the coil end is provided as centrally as possible.

FIG. 7 shows another embodiment of the chip inductor according to the present invention. As in the embodiment shown in FIG. 1, a coil member 34 having a coil 32 formed of a spiral conductive film on the outer circumferential surface of the insulating base 30 in the longitudinal direction, and both ends of the coil member 34 so as to be connected to the coil ends, respectively. And an insulating layer 38 for protecting the outer periphery of the coil 32. The insulating base 30 has a rectangular parallelepiped shape having the same cross-sectional shape over its entire length, and the chip thickness / chip width of the chip cross-sectional shape orthogonal to the coil axis is less than 1. The external electrodes 36 are formed on both wide surfaces of the coil member 34 so as to cover a part of the insulating layer 38.
It is plated with a material 40 having good solder wettability, including other exposed portions of the conductor film.

In this embodiment, the coil 32 is
0, and is formed over almost the entire length of the insulating base 30 to the inside of the external electrode 36, except for the vicinity of both ends of 0.
Both end surfaces of the coil member 34 are non-conductive surfaces. The external electrodes 36 are formed at both ends of the wide upper and lower surfaces, and can be surface-mounted on the circuit board in any direction.

In the present invention, since the insulating base 30 has the same rectangular parallelepiped shape over the entire length thereof,
The coil 32 is not limited to the region between the external electrodes 36, and can be formed over substantially the entire length of the insulating base 30. Therefore, the number of turns can be increased, and high inductance can be realized. Therefore, it is possible to handle a wide range from low inductance to high inductance. Further, when the number of turns is small, the conductor width can be widened, so that the resistance becomes low.

Further, in the configuration in which the coil 32 is formed over substantially the entire length of the insulating base 30, a magnetic field is hardly leaked on the way and is radiated outside from the end of the coil (see FIG. 5A). In the present embodiment, there is no conductor film on the end face of the coil member 34 and, therefore, the magnetic field is not interrupted, so that the loss is small and the Q value can be increased.

When there is no conductor film on the end face of the chip as in this embodiment, when the coil is formed only in the central portion, since the external electrode exists in the portion where the magnetic field is strong, the curve c in FIG. The frequency-Q value characteristic as shown is obtained. On the other hand, as shown in FIG. 7, when the coil is formed over almost the entire length up to the chip end face, there is no conductor in the portion where the magnetic field is strong, and the frequency-Q value characteristic is improved as shown by the curve d in FIG. Therefore, when there is no conductor film on the end face of the chip, it is preferable to form the coil using almost the entire length of the chip as much as possible, even if the number of turns is small.

FIG. 9 shows another embodiment of the chip type inductor according to the present invention. As in the embodiment shown in FIG. 7, a coil member 34 having a coil 32 made of a spiral conductive film formed on the outer circumferential surface of the insulating base 30 in the longitudinal direction, and both ends of the coil member 34 so as to be connected to the coil ends, respectively. And an insulating layer 38 for protecting the outer periphery of the coil 32. The insulating base 30 has a rectangular parallelepiped shape having the same cross-sectional shape over its entire length, and the chip thickness / chip width of the chip cross-sectional shape orthogonal to the coil axis is less than 1. The coil 32 is formed over substantially the entire length of the insulating base 30 up to the inside of the external electrode 36, leaving only the vicinity of both ends of the insulating base 30, and both end faces of the coil member 34 are non-conductive surfaces. The external electrodes 36 are formed on both wide surfaces of the coil member 34 so as to cover a part of the insulating layer 38, and are plated with a material 40 having good solder wettability, including other exposed portions of the conductor film. .

In this embodiment, the external electrodes 36 are formed at both ends of one of the two wide surfaces (the lower surface).
On the opposite wide surface, a flat insulating layer 39 of a color different from the other side surfaces is provided. Therefore, the surface on which the external electrodes 36 are formed is the mounting surface, and faces the circuit board. Vacuum suction is performed on the opposite flat surface of a different color, and the surface is mounted. Vacuum suction is automatically performed by recognizing a difference in color. In this structure, since only one surface needs to be flattened, the resin coating operation can be further simplified.

The external electrode 36 is formed only on one wide surface, and not on the other surface. When the coil 32 is formed over substantially the entire length of the coil member 34, it is preferable that the coil end has as few conductors as possible as described above. Therefore, in the configuration as in the present embodiment, the Q value can be further increased by removing an unnecessary portion of the conductor film irrelevant to the coil in the vicinity of both ends of the surface coated with the resin of a different color. Can be.

In the case of this embodiment, it is preferable that the conductor film is not formed not only on the chip end face but also near the chip end. FIG. 10 shows a top view of the coil member 34 in that case. Reference numeral 42 denotes a portion where the conductor film is removed near the end and the material of the insulating base is exposed. The removal of the conductor film can be easily performed by laser processing, similarly to the coil formation. With this configuration, the frequency-Q value characteristic is further improved (see the curve e in FIG. 11). This characteristic is the characteristic of a structure in which a coil is formed in the center and a conductor film is provided on the end face of the chip (FIG.
1 (see curve f)).

Next, the manufacturing procedure of the chip type inductor according to the present invention will be described. FIG. 12 shows an example of a manufacturing process of a chip-type inductor having a structure corresponding to FIG. The following order corresponds to the reference numbers in the drawings. (1) The conductor film 52 is formed on the entire outer surface (six surfaces) of the rectangular parallelepiped insulating base 50. Alumina ceramic was used for the insulating substrate 50, and the conductor film 52 was formed by copper plating. The insulating substrate 50 was designed to obtain a final chip size of 1.0 mm in length, 0.5 mm in width, and 0.35 mm in thickness, so that the same equipment as used for manufacturing chip resistors could be used. (2) Next, a spiral cut groove 54 was formed on the outer peripheral surface by laser processing to produce a coil 56. Here, since the conductor film is still formed on both end surfaces of the insulating base, the coil 56 is formed only in the region between the external electrode forming portions. This is the coil member 58. (3) Two wide opposing surfaces (upper and lower surfaces) of the coil member 58
External electrodes 60 are formed at both end portions of the substrate. External electrode 60
Was formed by thickly transferring and heat-curing a conductive resin in which silver particles and an epoxy resin were mixed. (4) A region between the external electrodes 60 is coated with an epoxy resin layer 62 so as to protect the coil. This resin coat is to make the wide surface flat. For example, it may be formed by printing, or may be flattened by pressing a flat member after application. Then, it is cured by heating. (5) Finally, not only the external electrodes but also the exposed portions of the conductor film are plated with a material 64 having good solder wettability. Here, all the conductor surfaces were plated with nickel and further plated with solder.

The order of the steps (3) and (4) may be reversed. In any case, this structure is limited to only two mountable surfaces, and is easier to manufacture than a conventional structure in which external electrodes are formed thick on the entire outer periphery and a flat insulating layer is formed on the entire outer periphery.

FIG. 13 shows an example of a process for manufacturing a chip inductor having a structure corresponding to FIG. The following procedures correspond to the reference numerals in the drawings. (1) The conductor film 52 is formed on the entire outer surface (six surfaces) of the rectangular parallelepiped insulating base 50. Alumina ceramic was used for the insulating substrate 50, and the conductor film 52 was formed by copper plating. The purpose of the insulating substrate 50 was to obtain a final chip size of 1.0 mm in length, 0.5 mm in width, and 0.35 mm in thickness. (2) Next, the conductor films on both end surfaces were removed by polishing or the like to expose the base of the insulating base 50. (3) Then, a spiral cut groove 54 was formed on the outer peripheral surface by laser processing to produce a coil 56. Here, the coil 56 is formed over substantially the entire length of the insulating base 50. Of course, in order to connect to the external electrode in a later step, 0.03 mm or more of the end portion needs to be left as a conductive film. This is the coil member 58. (4) The epoxy resin layer 62 is coated so as to protect the coil 56 except for both ends. This resin coat is to make the wide surface flat. For example, it may be formed by printing, or may be flattened by pressing a flat member after application. (5) Wide opposing two surfaces (upper and lower surfaces) of the coil member 58
External electrodes 60 are formed at both end portions of the substrate. External electrode 60
Is formed by thickly transferring and heat-curing a conductive resin in which silver particles and an epoxy resin are mixed so as to include the conductive film at the end of the coil member 58 and the end of the epoxy resin layer 62. (6) Finally, not only the external electrodes 60 but also other exposed portions of the conductive film are plated with a material 64 having good solder wettability. Here, nickel plating and solder plating were performed on all conductor surfaces. Therefore, both ends of the chip are finally in a state where the base of the insulating base 50 is exposed (that is, no conductor).

In such a structure, almost the entire chip is used for forming the coil, so that a high inductance can be obtained, and since there is no conductor on the end face, Q
The value increases.

In addition, instead of removing the conductor films on both end surfaces of the rectangular parallelepiped insulating base, a method of forming a conductor film on the outer peripheral surface of a rod-shaped insulator and cutting the same at a predetermined length is also used.
A product similar to that obtained in the step (3) can be manufactured.

FIG. 14 shows an example of a process for manufacturing a chip inductor having a structure corresponding to FIG. The following procedures correspond to the reference numerals in the drawings. (1) The conductor film 52 is formed on the entire outer surface (six surfaces) of the rectangular parallelepiped insulating base 50. Alumina ceramic was used for the insulating substrate 50, and the conductor film 52 was formed by copper plating. The insulating substrate has a length of 1.0 mm, a width of 0.5 mm, and a thickness of 0.1 mm.
Designed for a final chip size of 35 mm. (3) Next, the conductor films on both end faces are deleted, and the insulating substrate 50 is removed.
The base was exposed. (3) Spiral cut grooves 54 on the outer peripheral surface by laser processing
Was formed to produce a coil 56. Here, the insulating substrate 50
Was formed over substantially the entire length of the coil. Of course, in order to connect with the external electrode, 0.0
It is necessary to leave the conductor film of 3 mm or more as a conductor film. Also,
The conductors at both ends of the opposite wide surface that are not related to the coil are deleted so as not to disturb the magnetic field as much as possible. (4) The epoxy resin layer 62 is coated so as to protect the coil 56 except for both ends. In this resin coat, one wide surface and both narrow surfaces may have the same color, but the other wide surface has a different color to facilitate recognition. This resin coat makes the wide surface of the different color flat. For example, it may be formed by printing, or may be flattened by pressing a flat member after application. The resin layers having different colors are indicated by reference numeral 63. (5) External electrodes 60 are formed only on both ends of one wide surface (the lower surface of the same color as the side surface) of the coil member 58.
The external electrode 60 is formed by thickly transferring and heat-curing a conductive resin obtained by mixing silver particles and an epoxy resin so as to include the conductive film at the end of the coil member 58 and the end of the resin layer. (6) Finally, not only the external electrodes but also other exposed portions of the conductive film are plated with a material 64 having good solder wettability. Here, nickel plating and solder plating were performed on all conductor surfaces. Therefore, both end surfaces of the chip are in a state where the material of the insulating base is exposed.

In such a structure, almost the entire chip is used for forming the coil, so that a high inductance can be obtained. Further, since there is no conductor not only at the end face but also at the end of the upper face, the Q is further improved. The value can be higher.

[0043]

As described above, according to the present invention, the insulating substrate has a rectangular parallelepiped shape having the same cross-sectional shape over its entire length, and the chip thickness / chip width of the chip cross-sectional shape orthogonal to the coil axis is less than 1. Because of the shape, the surface on which the insulating layer is to be planarized can be reduced, so that the process can be simplified and the production becomes easy. In addition, by using the shape anisotropy, the parts can be supplied in the same direction by the parts feeder, so that the bag can be packed without taping, the cost can be reduced, and no packaging waste is generated.

Further, since the coil can be formed over almost the entire length of the chip, the required inductance range can be widened. When the number of turns is small, the conductor width can be widened, so that the resistance can be reduced. Further, laser processing can be facilitated and short circuit can be prevented, so that the yield is increased and the reliability is also increased.

Further, according to the present invention, since the coil member is formed without the conductive film on the end face of the coil member and the coil can be formed over substantially the entire length of the chip, the magnetic field is hardly interrupted, and the Q value is significantly increased. can do.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a chip-type inductor according to the present invention.

FIG. 2 is an explanatory view showing another example of the structure of the insulating layer.

FIG. 3 is an explanatory view showing deformation of a conductive film.

FIG. 4 is a top view showing another structure of the coil member.

FIG. 5 is an explanatory diagram showing a relationship between a coil length and a magnetic flux density distribution.

FIG. 6 is a graph showing a characteristic change according to a coil length when a conductor is present on a chip end surface.

FIG. 7 is an explanatory view showing another embodiment of the chip inductor according to the present invention.

FIG. 8 is a graph showing a characteristic change according to a coil length when there is no conductor on a chip end surface.

FIG. 9 is an explanatory view showing still another embodiment of the chip-type inductor according to the present invention.

FIG. 10 is a top view showing the structure of the coil member.

FIG. 11 is a graph showing the frequency-Q value characteristics.

FIG. 12 is a view illustrating a manufacturing process of one embodiment of the chip-type inductor according to the present invention.

FIG. 13 is a view illustrating a manufacturing process of a chip-type inductor according to another embodiment of the present invention.

FIG. 14 is an explanatory view of a manufacturing process of still another embodiment of the chip-type inductor according to the present invention.

[Description of Signs] 10 Insulating base 12 Coil 14 Coil member 16 External electrode 18 Insulating layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E070 AA01 CA11 CC00 EA00

Claims (12)

[Claims] 1. A coil member having a coil formed of a spiral conductive film formed on an outer circumferential surface of an insulating base in a longitudinal direction, external electrodes provided at both ends of the coil member so as to be connected to coil ends, respectively. A chip-type inductor having an insulating layer for protecting the outer periphery of a coil, wherein the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over the entire length thereof, and a chip thickness / chip having a chip cross-sectional shape orthogonal to the coil axis. A chip type inductor having a width of less than 1. 2. A coil member in which a coil made of a spiral conductive film is formed on a longitudinal outer peripheral surface of an insulating base, external electrodes provided at both ends of the coil member so as to be connected to coil ends, respectively. A chip-type inductor having an insulating layer for protecting the outer periphery of a coil, wherein the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over the entire length thereof, and a chip thickness / chip having a chip cross-sectional shape orthogonal to the coil axis. The external electrode has a width of less than 1, and the external electrode is formed thicker than the insulating layer on both wide surfaces of the coil member, and is plated with a material having good solder wettability, including other exposed portions of the conductive film. A chip type inductor characterized by the above-mentioned. 3. A first insulating layer covering the outer peripheral four side surfaces of the coil member, and the first insulating layer having a wider surface than the coil member and having a flat surface is provided only on the first insulating layer on both of the wide surfaces. 2
3. The chip-type inductor according to claim 2, wherein said insulating layer is formed. 4. A coil member in which a coil made of a spiral conductive film is formed on an outer circumferential surface of an insulating base in a longitudinal direction, external electrodes provided on both ends of the coil member so as to be connected to coil ends, respectively. A chip-type inductor having an insulating layer for protecting the outer periphery of a coil, wherein the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over the entire length thereof, and a chip thickness / chip having a chip cross-sectional shape orthogonal to the coil axis. The width of the external electrode is less than 1, and the external electrode is formed to be thicker than the insulating layer only on one wide surface of the coil member, and is plated with a material having good solder wettability, including other exposed portions of the conductor film. Wherein the other wide side has a different color from the other side. 5. The chip-type inductor according to claim 4, wherein conductor-free portions are formed at both ends of the wide surface of the coil member facing the external electrode formation surface. 6. The first insulating layer covers the four outer peripheral sides of the coil member, and is wider than the coil member only on the wide first insulating layer facing the external electrode formation surface. The second has a flat surface and a different color from the first insulating layer.
6. The chip-type inductor according to claim 4, wherein said insulating layer is formed. 7. The chip-type inductor according to claim 3, wherein the first insulating layer is made of a low-temperature sintered ceramic, and the second insulating layer is made of a heat-resistant resin. 8. The chip type according to claim 1, wherein the coil is formed only in a region between the two external electrode forming portions, and both end surfaces of the coil member are covered with a conductor. Inductor. 9. A coil member in which a coil made of a spiral conductive film is formed on an outer circumferential surface of an insulating base in a longitudinal direction, external electrodes provided at both ends of the coil member so as to be connected to coil ends, respectively. In a chip-type inductor having an insulating layer for protecting an outer periphery of a coil, the insulating base has a rectangular parallelepiped shape having the same cross-sectional shape over the entire length thereof, and the coil is left only near both ends of the insulating base. A chip-type inductor which is formed over substantially the entire length of an insulating base up to the inside of an external electrode, and both end surfaces of a coil member are non-conductive surfaces. 10. The chip-type inductor according to claim 9, wherein the chip thickness / chip width of the chip cross-sectional shape orthogonal to the coil axis is less than 1. 11. The chip-type inductor according to claim 1, wherein the external electrode comprises a cured film of a mixture of conductive particles and epoxy resin. 12. An exposed portion of an insulating base is provided at a part of an external electrode forming portion near both ends of a coil member, and an external electrode is formed on both the exposed portion of the insulating base and the conductive film. The chip inductor according to claim 1, wherein: