JP2018026793A - Antenna element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna element capable of achieving little influence of a conductor provided at a circuit board in a packaging destination and suppression of increases in the layer number of base material layers and element thickness.SOLUTION: An antenna element 101A includes: a base material 1 of insulator ceramic; planar terminal electrodes 21, 22 formed on a first surface S1 of the base material 1; a coil conductor formed on the base material 1 and connected with the terminal electrodes 21, 22; and insulation ceramic films 31, 32 formed on a surface of the base material 1 and covering an outer edge part of the terminal electrodes 21, 22.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an antenna element including a coil antenna, and more particularly to a chip-like antenna element mounted on a circuit board or the like.

  Patent Document 1 discloses a chip-shaped antenna element in which a coil conductor is provided in a laminate in which a plurality of base material layers are laminated. Patent Document 1 discloses an antenna element in which a coil winding axis is parallel to a mounting surface and a conductive layer parallel to the mounting surface is provided outside the coil winding region. .

International Publication No. 2013/094667

  In general, when an antenna element is mounted on a circuit board having a conductor extending in a plane shape, such as a ground conductor pattern, the electrical characteristics such as inductance of the antenna element change due to the influence of the conductor provided on the circuit board.

  If it is an antenna element provided with a conductive layer as shown in Patent Document 1, if the antenna element is mounted so that the conductive layer is located between the coil conductor of the antenna element and the conductor of the circuit board, The change in the electrical characteristics can be reduced.

  However, in the antenna element including the conductive layer, a base material layer for forming a conductive layer is necessary, and the number of stacked layers increases and the thickness dimension increases.

  An object of the present invention is to provide an antenna element that is hardly affected by a conductor included in a circuit board on which the circuit is mounted and that suppresses an increase in the number of base layers and the element thickness.

(1) The antenna element of the present invention is
An insulating ceramic substrate;
A plurality of planar terminal electrodes formed on the first surface of the substrate;
A coil conductor forming a coil antenna, formed on the base material and connected to at least two terminal electrodes of the plurality of terminal electrodes;
An insulating ceramic film formed on a surface of the base material and covering at least a part of an outer edge portion of at least one terminal electrode among the plurality of terminal electrodes;
It is characterized by providing.

  The coil conductor may be entirely formed inside the base material, a part may be formed on the surface of the base material, and the rest may be formed inside the base material.

  Since the terminal electrode of the antenna element is located between the coil conductor of the antenna element and the conductor of the circuit board, increasing the area of the terminal electrode increases the shielding effect of the terminal electrode, and the electrical characteristics of Change can be reduced. However, since there are a plurality of terminal electrodes and the distance between the terminal electrodes becomes narrow, there is a possibility that the terminal electrodes are short-circuited (bridged) with solder when the antenna element is mounted.

  According to the above configuration of the present invention, even when the area of the terminal electrode is increased, at least a part of the outer edge portion of at least one terminal electrode among the plurality of terminal electrodes is covered with the insulating ceramic film. Is suppressed.

(2) It is preferable that the insulating ceramic film covers an outer edge portion of the adjacent terminal electrodes in a portion where the interval between the adjacent terminal electrodes is the shortest distance among the plurality of terminal electrodes. Thereby, the short circuit in the position between terminal electrodes with the highest short circuit risk is suppressed, and effective short circuit suppression is made.

(3) In (1), it is preferable that the insulating ceramic film covers the entire outer edge of at least one of the plurality of terminal electrodes. Thereby, a short circuit risk is suppressed over a wide range, and effective short circuit suppression is performed.

(4) The substrate has an end surface perpendicular to the first surface, a part of the coil conductor is exposed on a surface of the end surface, and the insulating ceramic film is at least one terminal of the plurality of terminal electrodes. It is preferable to cover at least a part of the outer edge portion close to the end face of the electrode. Thereby, the distance of the coil conductor exposed to an end surface and the outer edge of the exposed part of the terminal electrode which adjoins this is ensured, and effective short circuit suppression is made. In particular, in a structure in which a part of the coil conductor is exposed on the end face of the base material, there is a risk of chipping in the vicinity of the ridge between the end face and the first surface. Even if this chipping occurs, the short circuit is suppressed.

(5) The total area of the plurality of terminal electrodes is preferably 25% or more of the area of the first surface. Thereby, the shielding effect by a terminal electrode can be utilized effectively.

(6) The shortest distance between the plurality of terminal electrodes is preferably 1.5 mm or less. Thereby, the total area of a terminal electrode becomes large and the shield effect by a terminal electrode can be utilized effectively.

(7) It is preferable that the plurality of terminal electrodes have a portion overlapping the coil conductor in a plan view of the first surface. Thereby, the shielding effect by a terminal electrode can be utilized.

(8) There are three or more terminal electrodes, and among the plurality of terminal electrodes, for example, at least one terminal electrode does not conduct with the coil conductor. This effectively acts also on a short circuit between the terminal electrode connected to the coil conductor and the terminal electrode not connected to the coil conductor.

  According to the present invention, it is possible to obtain an antenna element that is not easily affected by a conductor included in a circuit board to be mounted without increasing the number of base layers and the element thickness.

FIG. 1 is a simplified cross-sectional view of the antenna element according to the first embodiment mounted on a circuit board. FIG. 2 is a perspective view of the antenna element 101A according to the first embodiment. FIG. 3A is a plan view of the antenna element 101A on the first surface S1 side. FIG. 3B is a plan view of a comparative antenna element that does not have the insulating ceramic films 31 and 32. FIG. 4 is a plan view of the first surface S1 side of another antenna element 101B of the first embodiment. FIG. 5 is a simplified cross-sectional view of an antenna element 102A according to the second embodiment. FIG. 6A is a plan view of the antenna element 102A on the first surface S1 side. FIG. 6B is a plan view of an antenna element of a comparative example that does not have the insulating ceramic films 31 and 32. FIG. 7 is a plan view on the first surface S1 side of another antenna element 102B of the second embodiment. FIG. 8 is a perspective view of the antenna element 103 according to the third embodiment. FIG. 9 is a front view and a bottom view of the antenna element 103. 10 is a cross-sectional view taken along the line AA of the antenna element 103 shown in FIG. FIG. 11 is a perspective view of the antenna element 104 of the fourth embodiment. FIG. 12 is an exploded plan view showing electrode patterns and the like of each base material layer of the base material 1 constituting the antenna element 104. FIG. 13A is a plan view of the first surface S1 side of the antenna element 104 of the fourth embodiment. FIG. 13B is a plan view of a comparative antenna element that does not have the insulating ceramic films 31, 32, 33, and 34.

  Hereinafter, several specific examples will be given with reference to the drawings to show a plurality of modes for carrying out the present invention. In each figure, the same reference numerals are assigned to the same portions. In consideration of ease of explanation or understanding of the main points, the embodiments are shown separately for convenience, but partial replacement or combination of configurations shown in different embodiments is possible. In the second and subsequent embodiments, description of matters common to the first embodiment is omitted, and only different points will be described. In particular, the same operation effect by the same configuration will not be sequentially described for each embodiment.

  The “antenna element” shown in each embodiment can be applied to either a signal (or power) transmission (power transmission) side or a reception (power reception) side. Even when this “antenna element” is described as an antenna that radiates magnetic flux, the antenna element is not limited to being a magnetic flux generation source. Even when the transmission counterpart antenna element receives the magnetic flux generated (interlinks), that is, even if the transmission / reception relationship is reversed, the same effect is obtained.

  The “antenna element” shown in the following embodiments is an antenna element used for near-field communication using magnetic field coupling with a communication partner antenna element, or a near field using magnetic coupling with a power transmission counterpart antenna element. It is an antenna element used for the electric power transmission in. In the case of communication, it is applied to a communication system such as NFC (Near field communication). In the case of power transmission, it is applied to a power transmission system such as an electromagnetic induction method or a magnetic field resonance method. That is, the “antenna element” shown in each embodiment is used in a wireless transmission system such as communication or power transmission using at least magnetic field coupling. Note that the “antenna element” shown in each embodiment includes those that are wirelessly transmitted by electromagnetic field coupling (magnetic field coupling and electric field coupling) substantially with the transmission-side antenna element.

  As the “antenna element” shown in each embodiment, for example, the HF band, particularly 13.56 MHz, 6.78 MHz, or a frequency band in the vicinity thereof is used.

<< First Embodiment >>
FIG. 1 is a simplified cross-sectional view of the antenna element according to the first embodiment mounted on a circuit board. As shown in FIG. 1, the antenna element 101 </ b> A is mounted on the circuit board 90. The antenna element 101 </ b> A is provided with a coil conductor 10 constituting a coil antenna inside the substrate 1. The first surface S1 of the substrate 1 is a mounting surface that faces the circuit board 90. Terminal electrodes 21 and 22 are formed on the first surface S1. Both ends of the coil conductor 10 are connected to terminal electrodes 21 and 22.

  The circuit board 90 includes a conductor portion 91 having a large area such as a ground conductor pattern. Since the terminal electrodes 21 and 22 of the antenna element 101 </ b> A are between the coil conductor 10 and the conductor portion 91, the electrical characteristics of the antenna element 101 </ b> A are not easily affected by the conductor portion 91.

  FIG. 2 is a perspective view of the antenna element 101A according to the present embodiment. In the antenna element 101A, a flat rectangular helical coil conductor 10 is provided on a base 1. The coil conductor 10 includes a plurality of linear conductors 16 and 18 and a plurality of interlayer connection conductors 14 and 15 formed inside the substrate 1. The linear conductor 16 is formed inside the substrate 1 along the first surface S1 of the substrate 1. The linear conductor 18 is formed inside the base material 1 along the second surface S <b> 2 of the base material 1. The interlayer connection conductor 14 is formed inside the base material 1 along the end surface S3. The interlayer connection conductor 15 is formed inside the base material 1 along the end surface S4.

  The terminal electrodes 21 and 22 are exposed on the first surface S1 of the substrate 1 and are connected to both ends of the coil conductor 10, respectively.

  As shown in FIG. 2, the length dimension of the antenna element 101A in the coil axis direction of the coil conductor 10 is L, the width dimension of the antenna element 101A in the width direction of the coil opening of the coil conductor 10 is W, and the coil opening of the coil conductor 10 is When the height dimension of the antenna element 101A in the height direction is represented by H, it is preferable that H <W <L.

  FIG. 3A is a plan view of the antenna element 101A on the first surface S1 side. FIG. 3B is a plan view of a comparative antenna element that does not have insulating ceramic films 31 and 32 to be described later.

  The antenna element 101 </ b> A is formed on an insulating ceramic base material 1, planar terminal electrodes 21 and 22 formed on the first surface S <b> 1 of the base material 1, and the inside or the surface of the base material 1. , 22 and a coil conductor 10 connected thereto. The terminal electrodes 21 and 22 overlap a part of the coil conductor 10 in a plan view of the first surface S1.

  On the surface of the substrate 1, rectangular frame-shaped insulating ceramic films 31 and 32 that cover the outer edges of the terminal electrodes 21 and 22 are formed. The base material 1 is a laminated body of insulator ceramics such as LTCC (Low Temperature Co-fired Ceramics). This laminate is obtained by laminating LTCC green sheets, heating and pressurizing to form a laminate, and firing the laminate. More specifically, a predetermined conductor pattern is formed by printing a Cu paste on a green sheet of LTCC, these green sheets are laminated, heated and pressurized to form a large-sized (collected substrate state) laminated body, An insulating ceramic paste is printed on the large laminate. Thereafter, the large laminate is divided into individual pieces and fired. Thereby, the base material 1, the coil conductor 10, and the insulating ceramic films 31 and 32 are formed.

  The distance G0 between the first terminal electrode 21 and the second terminal electrode 22 is equal in both the antenna element 101A of the present embodiment and the antenna element of the comparative example shown in FIG. In the antenna element 101A of the present embodiment, since the outer edge portions of the terminal electrodes 21 and 22 are covered with the insulating ceramic films 31 and 32, the interval between the exposed portions of the terminal electrodes 21 and 22 is G1. Since G1> G0, the risk of short circuit due to solder between the terminal electrodes 21 and 22 is reduced. That is, since the insulating ceramic films 31 and 32 have high resistance and low solder wettability, the distance between the terminal electrodes is G1 from the viewpoint of mountability, and a short circuit due to solder can be suppressed. Further, as described above, in the antenna element 101A, the relationship among the length dimension L, the width dimension W, and the height dimension H is H <W <L. As a result, a warp in which the L direction (coil axis direction) of the antenna element 101A is bent easily occurs. However, since the boundary between the terminal electrodes 21 and 22 and the substrate 1 is covered with the insulating ceramic films 31 and 32, the mechanical strength is improved. As a result, warpage of the antenna element 101A in the L direction is suppressed.

  FIG. 4 is a plan view on the first surface S1 side of another antenna element 101B of the present embodiment. The formation range of the insulating ceramic films 31 and 32 is different from that of the antenna element 101A shown in FIG. In the example shown in FIG. 3A, the insulating ceramic films 31 and 32 cover all of the outer edges of the terminal electrodes 21 and 22, but in the example shown in FIG. 21 and 22 are partially covered. In particular, the insulating ceramic films 31 and 32 are formed at positions adjacent to each other of the terminal electrodes 21 and 22.

  As described above, even if the insulating ceramic films 31 and 32 cover only the outer edges of the adjacent positions of the terminal electrodes 21 and 22, a short circuit due to solder can be suppressed.

  The total area of the terminal electrodes 21 and 22 is preferably 25% or more of the area of the first surface S1. More preferably, it is 50% or more. Thereby, the high shielding effect by a terminal electrode can be utilized. Moreover, it is preferable that the space | interval of an adjacent terminal electrode is 1.5 mm or less. Thereby, the shielding effect by a terminal electrode increases. With such a narrow interval, the risk of short circuit due to solder is high, but the formation of the insulating ceramic film increases the substantial distance between the terminal electrodes 21 and 22 and suppresses the risk of short circuit due to solder.

<< Second Embodiment >>
In 2nd Embodiment, it shows about an antenna element provided with the terminal electrode which does not conduct with a coil conductor.

  FIG. 5 is a simplified cross-sectional view of the antenna element 102A according to the present embodiment. As shown in FIG. 5, the antenna element 102 </ b> A is provided with a coil conductor 10 inside the base material 1. The first surface S1 of the base material 1 is a mounting surface that faces the mounting circuit board. Terminal electrodes 21, 22, 25 are formed on the first surface S1. Both ends of the coil conductor 10 are connected to terminal electrodes 21 and 22.

  FIG. 6A is a plan view of the antenna element 102A on the first surface S1 side. FIG. 6B is a plan view of an antenna element of a comparative example that does not have the insulating ceramic films 31 and 32.

  The antenna element 101A is formed on the insulating ceramic base material 1, the planar terminal electrodes 21, 22, 25 formed on the first surface S1 of the base material 1, and the inside or the surface of the base material 1, and the terminal And a coil conductor 10 connected to the electrodes 21 and 22. The terminal electrodes 21, 22, 25 overlap a part of the coil conductor 10 in a plan view of the first surface S 1.

  Insulating ceramic films 31, 32, and 35 are formed on the surface of the substrate 1 to cover the outer edges of the terminal electrodes 21, 22, and 25.

  FIG. 7 is a plan view on the first surface S1 side of another antenna element 102B of the present embodiment. The formation range of the insulating ceramic film is different from that of the antenna element 102A shown in FIG. In the example shown in FIG. 6A, the insulating ceramic films 31, 32, and 35 cover all of the outer edges of the terminal electrodes 21, 22, and 25. However, in the example shown in FIG. 25, the insulating ceramic film is covered only on a part of the outer edges. In this example, the insulating ceramic film 31 is covered on the outer edge of the terminal electrode 21 adjacent to the terminal electrode 25, and the insulating ceramic film 32 is covered on the outer edge of the terminal electrode 22 adjacent to the terminal electrode 25. Insulating ceramic films 35A and 35B are covered on the outer edges of the terminal electrodes 25 adjacent to the terminal electrodes 21 and 22, respectively.

  As described above, even if the insulating ceramic films 31 and 32 cover only the outer edges of the adjacent positions of the terminal electrodes 21 and 22, a short circuit due to solder can be suppressed.

  According to the present embodiment, the total area of the terminal electrodes 21, 22, 25 or the total area ratio of the terminal electrodes 21, 22, 25 to the area of the first surface S1 of the substrate 1 can be increased. , 25 can enhance the shielding effect. The total area of the plurality of terminal electrodes 21, 22, 25 is preferably 25% or more of the area of the first surface S1, and more preferably 50% or more. Thereby, the shielding effect by a some terminal electrode can be utilized.

<< Third Embodiment >>
In the third embodiment, an antenna element in which a part of a coil conductor is exposed on an end surface perpendicular to the first surface of the substrate will be described.

  FIG. 8 is a perspective view of the antenna element 103 of the present embodiment. FIG. 9 is a front view and a bottom view of the antenna element 103. In the antenna element 103, a flat rectangular helical coil conductor is provided on the base material 1. The end face conductor 10E which is a part of the coil conductor is exposed on the end faces S3 and S4 perpendicular to the first face S1 of the substrate 1. The first surface S1 of the substrate 1 is a mounting surface facing the circuit board, and terminal electrodes 21 and 22 are formed on the first surface S1. Both ends of the coil conductor are connected to terminal electrodes 21 and 22. The terminal electrodes 21 and 22 overlap a part of the coil conductor in a plan view of the first surface S1. Insulating ceramic films 31 and 32 are covered on the outer edges of the terminal electrodes 21 and 22.

  10 is a cross-sectional view taken along the line AA of the antenna element 103 shown in FIG. If the coil conductor has a structure in which a part of the coil conductor is exposed at the end face of the base material 1, the interface IF between the conductor pattern and the base material layer is exposed at the end face. . When such chip CH is generated, the end surface conductor 10E is exposed as viewed from the first surface S1 of the substrate 1. Therefore, when there is no insulating ceramic film 32, the space | interval of the end surface conductor 10E and the outer edge of the terminal electrode 22 will be shortened. In FIG. 10, the interval D0 is the interval in that case.

  In the present embodiment, since the outer edge of the terminal electrode 22 is covered with the insulating ceramic film 32, a substantial distance D1 between the conductor 10E on the end face and the terminal electrode 22 is ensured even if a chip CH is generated. In addition, the presence of the insulating ceramic film 32 improves the mechanical strength of the portion covered with the insulating ceramic film 32. Therefore, even if a chip CH is generated in the substrate 1, the size of the chip can be limited.

<< Fourth Embodiment >>
In the fourth embodiment, an antenna element including four terminal electrodes is shown.

  FIG. 11 is a perspective view of the antenna element 104 of the present embodiment. FIG. 12 is an exploded plan view showing electrode patterns and the like of each base material layer of the base material 1 constituting the antenna element 104.

  The antenna element 104 is an element in which an auxiliary coil conductor of about one turn and a flat rectangular helical coil conductor are formed on a rectangular parallelepiped substrate 1.

  Terminal electrodes 21, 22, 23, and 24 are formed on the lower surface of the base material layer 1a shown in FIG. The terminal electrodes 21, 22, 23, and 24 overlap a part of the coil conductor 10 in a plan view of the first surface S1 (see FIG. 11).

  Conductors 21B and 22B and linear conductors 11 and 11 are formed on the lower surface of the base material layer 1b shown in (2) of FIG. Conductors 21B and 22B and terminal electrodes 21 and 22 are connected to each other through interlayer connection conductors. The linear conductors 11 and 11 are connected to the terminal electrodes 23 and 24 through interlayer connection conductors, respectively.

  A plurality of linear conductors 16A are formed on the lower surface of the base material layer 1c shown in (3) of FIG. A plurality of linear conductors 16B are formed on the lower surface of the base material layer 1d shown in (4) of FIG. The plurality of linear conductors 16A and the plurality of linear conductors 16B are respectively connected in parallel via interlayer connection conductors.

  A plurality of end surface conductors 17 are formed on the base material layers 1e to 1o shown in (5) to (15) in FIG.

  A plurality of linear conductors 18B and one linear conductor 13B are formed on the lower surface of the base material layer 1p shown in (16) of FIG. A plurality of linear conductors 18A and one linear conductor 13A are formed on the lower surface of the base material layer 1q shown in (17) in FIG. The plurality of linear conductors 18A and the plurality of linear conductors 18B are respectively connected in parallel via interlayer connection conductors. Further, the linear conductor 13A and the linear conductor 13B are connected in parallel via an interlayer connection conductor.

  The plurality of linear conductors 16B are sequentially connected in series to the plurality of linear conductors 18B via the end surface conductors 17.

  The linear conductors 16A, 16B, 18A, 18B and the end face conductor 17 form a rectangular helical coil of about 12 turns.

  Further, the linear conductors 11, 11, 13A, 13B, the end face conductor 12, and the like form a rectangular loop coil of about one turn.

  FIG. 13A is a plan view of the antenna element 104 of the present embodiment on the first surface S1 side. FIG. 13B is a plan view of an antenna element of a comparative example that does not have insulating ceramic films 31, 32, 33, and 34 to be described later.

  On the first surface S <b> 1 of the base material 1, insulating ceramic films 31 and 32 covering the outer edges of the terminal electrodes 21 and 22 and insulating ceramic films 33 and 34 covering the outer edges of the terminal electrodes 23 and 24 are formed, respectively. .

  If the insulating ceramic film is formed so as to cover the outer edge of each terminal electrode for an antenna element including four or four or more terminal electrodes as in this embodiment, a short circuit due to solder can be suppressed.

  A continuous insulating ceramic film may be formed between adjacent terminal electrodes. For example, a continuous insulating ceramic film may be formed between the terminal electrode 23 and the terminal electrode 24.

  Moreover, in each embodiment shown above, although the coil winding axis showed the example parallel to 1st surface S1 (mounting surface), it is not restricted to this, A coil winding axis is orthogonal to a mounting surface. Or may be inclined with respect to the mounting surface.

  Finally, the description of the above embodiment is illustrative in all respects and not restrictive. Modifications and changes can be made as appropriate by those skilled in the art. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention includes modifications from the embodiments within the scope equivalent to the claims.

CH ... chip IF ... interface S1 ... first face S2 ... second face S3, S4 ... end face 1 ... base material 1a to 1q ... base material layer 10 ... coil conductor 10E ... end face conductors 11, 13A, 13B, 16, 16A, 16B, 18, 18A, 18B ... linear conductors 12, 17 ... end face conductors 14, 15 ... interlayer connection conductors 21, 22, 23, 24, 25 ... terminal electrodes 21B, 22B ... conductors 31-35 ... insulating ceramic film 35A, 35B ... Insulating ceramic film 90 ... Circuit board 91 ... Conductor portions 101A, 101B, 102A, 102B, 103, 104 ... Antenna elements

Claims (8)

An insulating ceramic substrate;
A plurality of planar terminal electrodes formed on the first surface of the substrate;
A coil conductor forming a coil antenna, formed on the base material and connected to at least two terminal electrodes of the plurality of terminal electrodes;
An insulating ceramic film formed on a surface of the base material and covering at least a part of an outer edge portion of at least one terminal electrode among the plurality of terminal electrodes;
An antenna element comprising:   2. The antenna element according to claim 1, wherein the insulating ceramic film covers an outer edge portion of the adjacent terminal electrodes in a portion where the distance between the adjacent terminal electrodes is the shortest distance among the plurality of terminal electrodes.   The antenna element according to claim 1, wherein the insulating ceramic film covers the entire outer edge portion of at least one terminal electrode among the plurality of terminal electrodes. The substrate has an end surface perpendicular to the first surface;
A part of the coil conductor is exposed on the surface of the end face,
4. The antenna element according to claim 1, wherein the insulating ceramic film covers at least a part of an outer edge portion close to the end face of at least one terminal electrode among the plurality of terminal electrodes. 5.   The antenna element according to any one of claims 1 to 4, wherein a total area of the plurality of terminal electrodes is 25% or more of an area of the first surface.   The antenna element according to claim 1, wherein the shortest distance between the plurality of terminal electrodes is 1.5 mm or less.   The antenna element according to any one of claims 1 to 6, wherein the plurality of terminal electrodes have a portion overlapping the coil conductor in a plan view of the first surface.   The antenna element according to any one of claims 1 to 7, wherein there are three or more terminal electrodes, and at least one terminal electrode of the plurality of terminal electrodes is not electrically connected to the coil conductor.

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