Optical communication module and laminated coil component

Abstract

An optical communication module (100) is provided that includes a laminated coil component and reduces loss in a high-frequency region. The optical communication module (100) includes: a substrate (60) having a pad (70) with a gold layer on its surface; and a laminated coil component (1) mounted on the substrate (60). The optical communication module (100) is characterized in that the laminated coil component (1) includes: a laminate (10) formed by laminating a plurality of insulating layers (31) in a lamination direction and having a coil (30) disposed therein; and an external electrode (20) disposed on a surface of the laminate (10) and electrically connected to the coil (30). The external electrode (20) includes: a gold film (25) located on the outermost layer of the external electrode (20), the gold film (25) of the external electrode (20) being bonded to the gold layer of the pad (70) of the substrate (60) via a gold-tin solder (50).

Description

Technical Field

[0001] The present invention relates to an optical communication module and a laminated coil component. Background Art

[0002] Patent Document 1 discloses a laminated coil component including: a laminated body formed by laminating a plurality of insulating layers and having a coil built therein; and external electrodes.

[0003] It is described that the laminated coil component has excellent high-frequency characteristics and that the transmission coefficient S21 at 40 GHz and 50 GHz is equal to or greater than a specific value.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2019-186255

[0005] In optical communication modules, optical transmitting modules (TOSA: Transmitter Optical Subassembly) are used, which have light-emitting elements such as laser diodes and EML (electric field absorption modulator integrated laser) inside and convert electrical signals into optical signals for transmission; optical receiving modules (ROSA: Receiver Optical Subassembly) are used, which have light-receiving elements represented by photodiodes inside and convert received optical signals into electrical signals; and bidirectional modules (BOSA: Bidirectional Optical Subassembly) that include the functions of both of the above.

[0006] An example of the structure of an optical communication module will be described using a case of a TOSA as an example.

[0007] Lead terminals for transmitting (transmitting) electrical signals are inserted into the TOSA, and electrical signals are introduced into the TOSA. A substrate is provided within the TOSA, and electronic components such as ICs and light-emitting elements serving as electrical-optical converters are mounted on the substrate.

[0008] The electrical signal introduced into the TOSA is converted into an optical signal via wiring, IC, and light-emitting elements within the substrate.

[0009] The laminated coil component described in Patent Document 1 is used in optical communication modules to prevent high-frequency signals from flowing into power lines when a DC voltage is applied to a laser diode or the like. This laminated coil component has nickel and tin coatings on its external electrodes and is mounted on a motherboard substrate on which an optical communication module, such as a TOSA, is also mounted, electrically connected to the wiring within the TOSA.

[0010] In recent years, the data transfer rates used in optical communications have increased significantly, leading to a demand for reduced losses in the frequency range above 60 GHz. In this range, the problem arises: losses due to the inductance component of the wiring length connecting the stacked coil component to the optical communication module cannot be ignored. Summary of the Invention

[0011] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an optical communication module including a laminated coil component and having reduced loss in a high-frequency region.

[0012] The optical communication module of the present invention comprises: a substrate having a solder pad with a gold layer on its surface; and a stacked coil component mounted on the above-mentioned substrate. The above-mentioned optical communication module is characterized in that the above-mentioned stacked coil component has: a stacked body, which is formed by stacking multiple insulating layers in a stacking direction and has a coil arranged inside; and an external electrode, which is arranged on the surface of the above-mentioned stacked body and is electrically connected to the above-mentioned coil, and the above-mentioned external electrode comprises: a gold film located on the outermost layer of the above-mentioned external electrode, and the above-mentioned gold film of the above-mentioned external electrode is joined to the above-mentioned gold layer of the above-mentioned solder pad of the above-mentioned substrate via gold-tin solder.

[0013] The stacked coil component of the present invention is a stacked coil component installed in the optical communication module of the present invention, and is characterized in that it has: a stacked body, which is formed by stacking multiple insulating layers in the stacking direction and has a coil arranged inside; and an external electrode, which is arranged on the surface of the above-mentioned stacked body and is electrically connected to the above-mentioned coil, and the above-mentioned external electrode has: a gold film located on the outermost layer of the above-mentioned external electrode.

[0014] According to the present invention, it is possible to provide an optical communication module including a laminated coil component and reducing loss in a high-frequency region. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram showing the internal and peripheral structures of the optical communication module of the present invention.

[0016] Figure 2 This is a schematic diagram showing the internal and peripheral structures of a conventional optical communication module.

[0017] Figure 3 It is a perspective view schematically showing an example of a laminated coil component.

[0018] Figure 4 It is a cross-sectional view schematically showing an example of a laminated coil component.

[0019] Figure 5 It schematically represents the composition Figure 4 Schematic exploded perspective view of the insulating layer of the laminated coil component shown.

[0020] Figure 6 It schematically represents the composition Figure 4 Schematic diagram of an exploded plan view of the insulating layer of the laminated coil component shown.

[0021] Description of Reference Numerals

[0022] 1, 1'... laminated coil component; 10... laminate; 11... first end surface; 12... second end surface; 13... first main surface; 14... second main surface; 15... first side surface; 16... second side surface; 20... external electrode; 20'... first external electrode having a tin coating on its surface; 21... first external electrode; 22... second external electrode; 23... base electrode layer; 24... nickel coating; 25... gold coating; 30... coil; 31, 31a, 31b, 31c, 31d, 35a, 35a1, 35a2, 35a3, 35a4, 35b, 35b1, 35b2, 35b3, 35b4... insulating layer; 32, 32a, 32b, 32c, 32d...coil conductor; 33a, 33b, 33c, 33d, 33p, 33q...via conductor; 36a, 36b, 36c, 36d...line portion; 37a, 37b, 37c, 37d...pad portion; 41...first connecting conductor; 42...second connecting conductor; 50...gold-tin solder; 60...substrate; 70...pad with a gold layer on the surface; 80...wiring; 90...external housing; 100, 100'...optical communication module (TOSA); 110...IC; 111...gold wire; 120...laser diode; 200...motherboard; 250...solder; 270...pad; 280...wiring between the IC and the stacked coil component. DETAILED DESCRIPTION

[0023] Hereinafter, the optical communication module and the laminated coil component according to the present invention will be described.

[0024] However, the present invention is not limited to the following structures and aspects, and can be applied with appropriate changes within the scope of the present invention. In addition, the present invention also includes a combination of two or more of the preferred structures and aspects of the present invention described below.

[0025] The substrate provided in an optical communication module such as a TOSA has pads with a gold layer on the surface, and electronic components are mounted on these pads. Generally, the electronic components are mounted on these pads using gold-tin solder.

[0026] The laminated coil component described in Patent Document 1 has a nickel coating and a tin coating on its external electrodes. However, it is not possible to mount an electronic component having such external electrodes on a pad having a gold layer on its surface via gold-tin solder.

[0027] Specifically, the laminated coil component described in Patent Document 1 cannot be directly mounted on a substrate provided in an optical communication module and having pads with a gold layer on the surface. Therefore, the laminated coil component must be mounted externally to the substrate, which increases the length of the wiring connecting the laminated coil component to the optical communication module.

[0028] Therefore, in the optical communication module of the present invention, a laminated coil component including a gold coating located on the outermost layer of the external electrode is used as the external electrode.

[0029] If the outermost layer of the external electrode is coated with gold, it can be mounted on the pad with the gold layer using gold-tin solder. Therefore, the laminated coil component can be directly mounted on the substrate of the optical communication module. This shortens the wiring length connecting the laminated coil component to other components of the optical communication module, reducing losses caused by the wiring's inductance. In other words, it is possible to provide an optical communication module equipped with a laminated coil component and having reduced losses in the high-frequency range.

[0030] An example of an embodiment of such an optical communication module will be described below.

[0031] Figure 1 Schematic diagram showing the internal and peripheral structures of the optical communication module of the present invention.

[0032] Figure 1 The optical communication module 100 shown is mounted on a motherboard 200. The optical communication module 100 includes an exterior housing 90 whose bottom surface serves as a substrate 60. The laminated coil component 1, IC 110, and laser diode 120 are mounted on the substrate 60. The optical communication module 100 includes the laser diode 120 as a light-emitting element, and thus functions as a transmitter optical signaling module (TOSA).

[0033] The IC 110 and the laser diode 120 are electronic components included in the optical communication module 100 , other than the laminated coil component 1 .

[0034] also, Figure 1 Schematically shows the interior of the exterior body 90 , and an arrow emitting light from the laser diode 120 is shown.

[0035] Substrate 60 includes pads 70 with a gold surface. IC 110 and laser diode 120 are mounted on pads 70 of substrate 60, respectively. Pads 70 are connected to IC 110 via gold wires 111, and pads 70 are connected to laser diode 120 via gold-tin solder 50. The connection between the electronic components and pads is not limited to the above-described method.

[0036] Regarding the structure of the pad 70 with a gold layer on the substrate 60, there is no particular limitation on its composition as long as the surface is a gold layer. Preferably, a nickel layer is present below the gold layer. If a nickel layer is present below the gold layer, solder corrosion can be prevented.

[0037] Alternatively, the pad 70 may be entirely made of a gold layer, or may be a pad made of copper with a nickel layer and a gold layer provided thereon.

[0038] As electronic components other than the laminated coil component 1 mounted on the substrate 60 , there may be mentioned, in addition to ICs and laser diodes, LED elements, photodiodes, resistors, capacitors, and the like.

[0039] When an optical communication module includes a light-receiving element such as a photodiode as an electronic component, it functions as a light receiving module (ROSA).

[0040] In addition, when the optical communication module includes a light emitting element and a light receiving element as electronic components, it functions as a bidirectional optical module (BOSA).

[0041] The laminated coil component 1 is mounted on the substrate 60 .

[0042] The details of the structure of the stacked coil component 1 will be described later, but the stacked coil component 1 includes: a stacked body 10, which is formed by stacking multiple insulating layers in a stacking direction and has a coil arranged inside; and an external electrode 20, which is arranged on the surface of the stacked body 10 and is electrically connected to the coil.

[0043] The external electrode 20 includes a gold coating located on the outermost layer of the external electrode 20. Details of the layer structure of the external electrode will be described later.

[0044] Furthermore, the laminated coil component 1 includes a first external electrode 21 and a second external electrode 22 as external electrodes 20 .

[0045] The gold coating provided on the external electrode 20 of the laminated coil component 1 is bonded to the gold layer on the surface of the pad 70 of the substrate 60 via the gold-tin solder 50 .

[0046] In the laminated coil component 1 , since the outermost layer of the external electrode 20 is a gold film, the gold-tin solder 50 can be used to bond the outer electrode 20 to the gold layer on the surface of the pad 70 .

[0047] The composition of the gold-tin solder is not particularly limited as long as it contains gold and tin, but compositions such as Au82Sn18, Au80Sn20, Au79Sn21, AuSn21.5, and Au78Sn22 can be used.

[0048] If the laminated coil component 1 can be bonded to the pad 70 having a gold layer on its surface, the laminated coil component 1 can be arranged in the optical communication module 100 .

[0049] Therefore, the wiring length of the wiring connecting the laminated coil component 1 and other electronic components arranged in the optical communication module 100 can be shortened.

[0050] In the optical communication module of the present invention, preferably, electronic components other than the laminated coil component are mounted on the substrate, and the electronic components are mounted adjacent to the laminated coil component.

[0051] In this specification, an electronic component and a laminated coil component are adjacent when no other electronic component exists between a straight line connecting the pads of the electrically connected laminated coil component and the pads of the electronic component at the shortest distance.

[0052] When the electronic component and the laminated coil component are mounted adjacent to each other, the wiring length connecting the electronic component and the laminated coil component is shortened, thereby further reducing the loss caused by the inductance component of the wiring.

[0053] Furthermore, in the optical communication module of the present invention, it is preferable that the electronic component mounted adjacent to the laminated coil component is an IC.

[0054] Figure 1 The laminated coil component 1 is shown mounted adjacent to an electronic component IC 110. The wiring length connecting the laminated coil component 1 and IC 110 is the length of the wiring 80 connecting the pad 70 on which the laminated coil component 1 is mounted and the pad 70 on which the IC 110 is mounted.

[0055] In order to Figure 1 The length of the wiring 80 shown is compared with the length of the wiring between the laminated coil component and the electronic component of the conventional optical communication module. Figure 2 Provide explanation.

[0056] Figure 2 This is a schematic diagram showing the internal and peripheral structures of a conventional optical communication module.

[0057] Figure 2 The optical communication module 100' shown is mounted on a mother substrate 200. The laminated coil component 1' is mounted on the mother substrate 200 outside the optical communication module 100'.

[0058] The laminated coil component 1' and Figure 1 The laminated coil components 1 shown differ in the structure of the external electrodes. The outermost surface of the external electrode 20 ′ is formed as a tin film.

[0059] The tin coating provided on the external electrode 20 ′ of the laminated coil component 1 ′ is bonded to the pad 270 of the motherboard 200 via the solder 250 .

[0060] The pads 270 of the motherboard 200 are not pads having a gold layer on the surface, and therefore are bonded to the external electrodes 20 ′ of the laminated coil component 1 ′ by the solder 250 which is not gold-tin solder.

[0061] exist Figure 2 In the illustrated embodiment, the wiring length connecting IC 110, an electronic component disposed in optical communication module 100′, to laminated coil component 1′ is increased. The wiring length connecting laminated coil component 1′ to IC 110 is the length of wiring 280 connecting pad 270 on which laminated coil component 1′ is mounted to pad 70 on which IC 110 is mounted.

[0062] If Figure 1 The length of the wiring 80 shown is Figure 2 Compared with the length of the wiring 280 shown, Figure 1 The wiring 80 shown is shorter. That is, the loss caused by the inductance component of the wiring can be reduced by the amount of the shortened length.

[0063] The optical communication module of the present invention has such a structure, thereby reducing the loss in the high-frequency range. The optical communication module is particularly suitable for use in the frequency range of 60 GHz or higher.

[0064] Next, a laminated coil component that can be used in the optical communication module of the present invention will be described.

[0065] The laminated coil components described below are also laminated coil components of the present invention.

[0066] The stacked coil component of the present invention is a stacked coil component installed in the optical communication module of the present invention, and is characterized in that it has: a stacked body, which is formed by stacking multiple insulating layers in the stacking direction and has a coil arranged inside; and an external electrode, which is arranged on the surface of the above-mentioned stacked body and is electrically connected to the above-mentioned coil, and the above-mentioned external electrode has: a gold film located on the outermost layer of the above-mentioned external electrode.

[0067] Figure 3 It is a perspective view schematically showing an example of a laminated coil component.

[0068] Figure 3 The laminated coil component 1 shown includes a laminate 10, a first external electrode 21, and a second external electrode 22. The laminate 10 is a roughly rectangular parallelepiped with six faces. The structure of the laminate 10 will be described later, but it is composed of multiple insulating layers stacked in the stacking direction and contains a coil. The first external electrode 21 and the second external electrode 22 are each electrically connected to the coil.

[0069] In the laminated coil component and laminated body in this specification, the length direction, height direction, and width direction are referred to as Figure 3 Here, the length direction (x direction), the height direction (y direction), and the width direction (z direction) are orthogonal to each other.

[0070] The longitudinal direction (x direction) is a direction parallel to the stacking direction.

[0071] like Figure 3 As shown, the stack 10 has: a first end face 11 and a second end face 12 opposite to each other in the length direction (x direction), a first main face 13 and a second main face 14 opposite to each other in the height direction (y direction) perpendicular to the length direction, and a first side face 15 and a second side face 16 opposite to each other in the width direction (z direction) perpendicular to the length direction and the height direction.

[0072] Figure 3 Although not shown, it is preferred that the laminate 10 have rounded corners and ridges. A corner is a portion where three surfaces of the laminate intersect, and a ridge is a portion where two surfaces of the laminate intersect.

[0073] The first external electrode and the second external electrode are external electrodes extending from at least a portion of the end surface of the stacked body to the main surface of the stacked body.

[0074] exist Figure 3 In the illustrated laminated coil component 1 , the first external electrode 21 covers a portion of the first end surface 11 of the laminate 10 and is arranged to extend from the first end surface 11 and cover a portion of the first main surface 13 .

[0075] also, Figure 3In the embodiment, the height of the portion of the first external electrode 21 covering the first end surface 11 of the stack 10 is constant, but as long as it covers a portion of the first end surface 11 of the stack 10, the shape of the first external electrode 21 is not particularly limited. For example, in the first end surface 11 of the stack 10, the first external electrode 21 may be in a bulging shape that becomes higher from the end toward the center. In addition, the length of the portion of the first external electrode 21 covering the first main surface 13 of the stack 10 is constant, but as it mainly covers a portion of the first main surface 13 of the stack 10, the shape of the first external electrode 21 is not particularly limited. For example, in the first main surface 13 of the stack 10, the first external electrode 21 may be in a bulging shape that becomes longer from the end toward the center.

[0076] like Figure 3 As shown, the first external electrode 21 may also extend from the first end face 11 and the first main face 13 to cover a portion of the first side face 15 and a portion of the second side face 16 .

[0077] In this case, it is preferable that the portion of the first external electrode 21 covering the first side surface 15 and the second side surface 16 is formed obliquely with respect to the ridgeline portion intersecting the first end surface 11 and the ridgeline portion intersecting the first main surface 13. Alternatively, the first external electrode 21 may be arranged so as not to cover a portion of the first side surface 15 or a portion of the second side surface 16.

[0078] exist Figure 3 In the illustrated laminated coil component 1 , the second external electrode 22 covers a portion of the second end surface 12 of the laminate 10 , and is arranged to extend from the second end surface 12 and cover a portion of the first main surface 13 .

[0079] Similar to the first external electrode 21 , the second external electrode 22 covers a region of the second end surface 12 including a ridge portion intersecting with the first main surface 13 .

[0080] As with the first external electrode 21, the shape of the second external electrode 22 is not particularly limited as long as it covers a portion of the second end surface 12 of the stack 10. For example, the second external electrode 22 may have a bulging shape that gradually increases in height from the end toward the center of the second end surface 12 of the stack 10. Furthermore, the shape of the second external electrode 22 is not particularly limited as long as it covers a portion of the first principal surface 13 of the stack 10. For example, the second external electrode 22 may have a bulging shape that gradually increases in height from the end toward the center of the first principal surface 13 of the stack 10.

[0081] The second external electrode 22 may also be arranged to extend from the second end face 12 and the first main surface 13, similarly to the first external electrode 21, and to cover a portion of the first side face 15 and a portion of the second side face 16. In this case, it is preferable that the portion of the second external electrode 22 covering the first side face 15 and the second side face 16 be formed obliquely with respect to the ridgeline intersecting the second end face 12 and the ridgeline intersecting the first main surface 13. Furthermore, the second external electrode 22 may be arranged so as not to cover a portion of the first side face 15 and a portion of the second side face 16.

[0082] Since the first external electrode 21 and the second external electrode 22 are arranged as described above, when the laminated coil component 1 is mounted on a substrate, the first principal surface 13 of the laminate 10 serves as a mounting surface.

[0083] Alternatively, it can be Figure 3 Unlike the embodiment shown, the first external electrode covers the entire first end surface of the laminate and extends from the first end surface to cover parts of the first main surface, the second main surface, the first side surface, and the second side surface.

[0084] Alternatively, the second external electrode may cover the entire second end surface of the laminate and extend from the second end surface to cover parts of the first main surface, the second main surface, the first side surface, and the second side surface.

[0085] In this case, any one of the first main surface, the second main surface, the first side surface, and the second side surface of the laminate serves as the mounting surface.

[0086] The external electrode has a gold coating located on the outermost layer of the external electrode.

[0087] As described above, if the outermost layer of the external electrode is a gold film, it is possible to bond it to the gold layer on the surface of the pad using gold-tin solder.

[0088] The thickness of the gold coating on the external electrode is preferably 0.4 μm or more and 1.2 μm or less, and more preferably 0.7 μm or more.

[0089] The external electrode preferably includes a nickel film located closer to the laminate than the gold film.

[0090] By having a nickel film on the inner side (laminate side) of the gold film, the nickel film can function as a barrier layer to prevent solder corrosion. Solder corrosion refers to the phenomenon in which layers further inward from the nickel film (including the silver base electrode layer) in the external electrode melt during soldering.

[0091] When the external electrode includes a nickel film, the thickness of the nickel film is preferably 1.5 μm or more and 4.5 μm or less.

[0092] The external electrode preferably includes a base electrode layer made of silver. The base electrode layer is preferably a layer in contact with the laminate.

[0093] Furthermore, as a structure of the external electrodes, it is preferable that a nickel film and a gold film are sequentially formed on a base electrode layer.

[0094] Since the external electrode includes the base electrode layer, the bonding strength between the laminate and the base electrode layer is high, and thus the bonding strength between the laminate and the external electrode can be improved.

[0095] The size of the laminated coil component is not particularly limited, but is preferably 0603 size, 0402 size, or 1005 size.

[0096] The insulating layer preferably includes a ferrite phase and a non-magnetic phase composed of a material having a lower dielectric constant than that of a ferrite material constituting the ferrite phase.

[0097] In addition, the insulating layer may be composed of only a ferrite phase or only a non-magnetic phase.

[0098] The ferrite phase may be a phase containing a ferrite material, or a phase composed only of a ferrite material.

[0099] The ferrite phase is preferably composed of a Ni—Cu—Zn ferrite material. Since the ferrite phase is composed of a Ni—Cu—Zn ferrite material, the inductance of the laminated coil component is improved.

[0100] The Ni-Cu-Zn ferrite material preferably comprises: 40 mol% to 49.5 mol% Fe2O3, 5 mol% to 35 mol% ZnO, 4 mol% to 12 mol% CuO, and the remainder NiO. These oxides may also contain unavoidable impurities.

[0101] The Ni-Cu-Zn ferrite material may also include additives such as Mn3O4, Bi2O3, Co3O4, and SnO2.

[0102] Furthermore, the ferrite phase preferably contains Fe when elemental analysis is performed, and includes Fe, Zn, Cu, and Ni. Furthermore, the ferrite phase may further include Mn, Bi, Co, Sn, and the like.

[0103] The preferred ferrite phase includes: Fe in an amount of 40 mol% to 49.5 mol% inclusive, calculated as Fe2O3, Zn in an amount of 2 mol% to 35 mol% inclusive, Cu in an amount of 6 mol% to 13 mol% inclusive, and Ni in an amount of 10 mol% to 45 mol% inclusive, calculated as NiO.

[0104] The non-magnetic phase is a phase composed of a material having a lower dielectric constant than that of the ferrite material.

[0105] Examples of materials constituting the non-magnetic phase include glass materials, forsterite (2MgO / SiO2), willemite [aZnO / SiO2 (a is 1.8 to 2.2)], etc. As the glass material, borosilicate glass is preferred.

[0106] Borosilicate glass preferably contains the following elements in the following proportions: Si converted into SiO2 is 80 wt% or more and 85 wt% or less, B converted into B2O3 is 10 wt% or more and 25 wt% or less, alkali metal A converted into A2O is 0.5 wt% or more and 5 wt% or less, and Al converted into Al2O3 is 0 wt% or more and 5 wt% or less. Examples of alkali metal A include K and Na.

[0107] The ferrite phase and non-magnetic phase are distinguished as follows. First, the laminated coil component is polished to expose a cross section along the lamination direction. Elemental mapping is then performed using scanning transmission electron microscopy-energy dispersive X-ray analysis (STEM-EDX). The region containing the Fe element is considered the ferrite phase, while the region other than the ferrite phase is considered the non-magnetic phase.

[0108] In addition, the cross section along the stacking direction is described later. Figure 4 The cross section shown.

[0109] With respect to the ferrite phase and the non-magnetic phase thus distinguished, the ferrite material constituting the ferrite phase has a high dielectric constant, while the material constituting the non-magnetic phase has a lower dielectric constant than that of the ferrite material.

[0110] The relative dielectric constant of the ferrite material is, for example, 14.5 or more and 15.5 or less.

[0111] The relative dielectric constant of the material constituting the non-magnetic phase is not limited as long as it is lower than that of the ferrite material, but is preferably 7.0 or less, and more preferably 5.0 or less, for example.

[0112] By including a non-magnetic phase made of a material with a lower dielectric constant than ferrite in the insulating layer constituting the laminated coil component, the dielectric constant of the insulating layer is reduced. The reduced dielectric constant of the insulating layer can reduce the loss of the laminated coil component itself.

[0113] To determine the relative dielectric constant of the ferrite material and the relative dielectric constant of the material constituting the non-magnetic phase, the structural formula of the ferrite material constituting the ferrite phase is determined through the above-mentioned elemental mapping, and the structural formula of the material constituting the non-magnetic phase is determined. Furthermore, the relative dielectric constant of the compound that corresponds to this structural formula is obtained from a known database. This procedure enables the relative dielectric constant of the ferrite material and the relative dielectric constant of the material constituting the non-magnetic phase to be determined separately.

[0114] Alternatively, a dielectric constant measurement sample may be prepared by molding a ferrite material into a predetermined shape, and after forming electrodes thereon, the capacitance may be measured under predetermined conditions. The relative dielectric constant of the ferrite material may be determined based on the capacitance measurement value and the dimensions of the dielectric constant measurement sample. Similarly, a dielectric constant measurement sample may be prepared by molding a material constituting a non-magnetic phase into a predetermined shape, and the relative dielectric constant of the material constituting the non-magnetic phase may be determined.

[0115] The volume ratio of the non-magnetic phase to the total volume of the ferrite phase and the non-magnetic phase is preferably 55 volume % or more and 80 volume % or less.

[0116] When the volume ratio of the non-magnetic phase to the total volume of the ferrite phase and the non-magnetic phase is less than 55 volume %, the amount of the material with a low relative dielectric constant is small, and therefore the effect of reducing the loss in the high-frequency region is correspondingly small.

[0117] On the other hand, when the volume ratio of the non-magnetic phase to the total volume of the ferrite phase and the non-magnetic phase exceeds 80 volume %, the ratio of the non-magnetic phase is too large, and thus the strength of the laminate may be insufficient.

[0118] From the viewpoint of improving the high-frequency characteristics of the laminated coil component, the volume ratio of the non-magnetic phase to the total volume of the ferrite phase and the non-magnetic phase is preferably 60 volume % or more and 80 volume % or less.

[0119] The volume ratio of the non-magnetic phase to the total volume of the ferrite phase and the non-magnetic phase is determined as follows: First, the laminate constituting the laminated coil component is ground to the center in a direction perpendicular to the lamination direction, thereby exposing a cross section along the lamination direction.

[0120] Next, after extracting three 50μm square areas near the center of the exposed cross section, element mapping was performed using a scanning transmission electron microscope-energy dispersive X-ray analysis to distinguish the ferrite phase from the non-magnetic phase as described above. Moreover, for each of the three areas mentioned above, based on the obtained element mapping images, the area ratio of the non-magnetic phase to the total area of ​​the ferrite phase and the non-magnetic phase was determined using image analysis software. Subsequently, based on the measured values ​​of these area ratios, the average value was calculated, and the average value became the volume ratio of the non-magnetic phase to the total volume of the ferrite phase and the non-magnetic phase.

[0121] Furthermore, the volume ratio of forsterite to the total volume of the non-magnetic phase is preferably 2 volume % or more and 8 volume % or less.

[0122] By distinguishing the region where the element contained in forsterite, namely the Mg element, as the region where forsterite exists, the area ratio of the region where forsterite exists relative to the area of ​​the non-magnetic phase is measured, thereby calculating the volume ratio of forsterite contained in the non-magnetic phase.

[0123] When 2% by volume or more and 8% by volume or less of the non-magnetic phase is forsterite, the strength of the laminate is improved.

[0124] The insulating layer preferably contains: B converted into B2O3 of more than 4.3 weight% and less than 8.0 weight%, Si converted into SiO2 of more than 27.6 weight% and less than 51.4 weight%, Mg converted into MgO of more than 1.1 weight% and less than 2.1 weight%, Fe converted into Fe2O3 of more than 24.7 weight% and less than 43.5 weight%, Ni converted into NiO of more than 3.3 weight% and less than 5.9 weight%, Zn converted into ZnO of more than 7.7 weight% and less than 13.5 weight%, and Cu converted into CuO of more than 2.0 weight% and less than 3.6 weight%.

[0125] The composition of the insulating layer was confirmed by analysis using inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0126] Next, an example of a coil built into a laminated body constituting a laminated coil component will be described.

[0127] The coil is formed by electrically connecting a plurality of coil conductors stacked together with insulating layers in a stacking direction.

[0128] Figure 4 is a cross-sectional view schematically showing an example of a laminated coil component. Figure 5 It schematically represents the composition Figure 4The exploded perspective view of the insulating layer of the laminated coil component shown in FIG. Figure 6 It schematically represents the composition Figure 4 Schematic diagram of an exploded plan view of the insulating layer of the laminated coil component shown.

[0129] Figure 4 The insulating layers, coil conductors, connecting conductors, and the stacking direction of the laminate are schematically shown, and do not strictly illustrate actual shapes, connection methods, etc. For example, the coil conductors are connected via via conductors.

[0130] like Figure 4 As shown, the laminated coil component 1 includes: a laminate 10 having a built-in coil formed by electrically connecting a plurality of coil conductors 32 laminated together with an insulating layer; and a first external electrode 21 and a second external electrode 22 electrically connected to the coil.

[0131] Figure 4 : It is shown that the first external electrode 21 and the second external electrode 22 include a base electrode layer 23 containing silver, and a nickel film 24 and a gold film 25 are formed in this order on the base electrode layer 23 .

[0132] The laminate 10 has a region where the coil conductor is arranged and a region where the first connecting conductor 41 or the second connecting conductor 42 is arranged. The lamination direction of the laminate 10 and the axial direction of the coil ( Figure 4 ) indicates that the coil axis A) is parallel to the first main surface 13 .

[0133] like Figure 5 and Figure 6 As shown, the laminate 10 includes an insulating layer 31a, an insulating layer 31b, an insulating layer 31c, and an insulating layer 31d. Figure 4 The laminate 10 includes an insulating layer 35a1, an insulating layer 35a2, an insulating layer 35a3, and an insulating layer 35a4. Figure 4 The laminate 10 includes an insulating layer 35b1, an insulating layer 35b2, an insulating layer 35b3, and an insulating layer 35b4. Figure 4 Insulating layer 35b.

[0134] The coil 30 includes a coil conductor 32a, a coil conductor 32b, a coil conductor 32c, and a coil conductor 32d. Figure 4 The coil conductor 32 in.

[0135] The coil conductor 32a, the coil conductor 32b, the coil conductor 32c, and the coil conductor 32d are respectively arranged on the main surfaces of the insulating layer 31a, the insulating layer 31b, the insulating layer 31c, and the insulating layer 31d.

[0136] The lengths of the coil conductors 32a, 32b, 32c, and 32d are each equal to the length of ¾ of a turn of the coil 30. In other words, the number of layers of coil conductors used to form three turns of the coil 30 is 4. In the laminate 10, the coil conductors 32a, 32b, 32c, and 32d are repeatedly laminated as a unit (three turns).

[0137] Coil conductor 32a includes a wire portion 36a and a pad portion 37a disposed at the end of wire portion 36a. Coil conductor 32b includes a wire portion 36b and a pad portion 37b disposed at the end of wire portion 36b. Coil conductor 32c includes a wire portion 36c and a pad portion 37c disposed at the end of wire portion 36c. Coil conductor 32d includes a wire portion 36d and a pad portion 37d disposed at the end of wire portion 36d.

[0138] Via-hole conductors 33a, 33b, 33c, and 33d are respectively arranged on the insulating layers 31a, 31b, 31c, and 31d so as to penetrate in the stacking direction.

[0139] The insulating layer 31a with the coil conductor 32a and the via-hole conductor 33a, the insulating layer 31b with the coil conductor 32b and the via-hole conductor 33b, the insulating layer 31c with the coil conductor 32c and the via-hole conductor 33c, and the insulating layer 31d with the coil conductor 32d and the via-hole conductor 33d are considered as a unit (by Figure 5 and Figure 6 The pads 37a of coil conductor 32a, 37b of coil conductor 32b, 37c of coil conductor 32c, and 37d of coil conductor 32d are thus connected via via-hole conductors 33a, 33b, 33c, and 33d. In other words, the pads of adjacent coil conductors in the stacking direction are connected to each other via via-hole conductors.

[0140] Based on the above, the solenoid-shaped coil 30 built into the laminated body 10 is configured.

[0141] When viewed from above in the stacking direction, the coil 30 composed of the coil conductors 32a, 32b, 32c, and 32d may have a circular or polygonal shape. When viewed from above in the stacking direction, if the coil 30 has a polygonal shape, the diameter of the circle equivalent to the area of ​​the polygon is used as the coil diameter of the coil 30, and the axis extending through the center of gravity of the polygon in the stacking direction is used as the coil axis of the coil 30.

[0142] Via conductors 33p are arranged on each of the insulating layers 35a1, 35a2, 35a3, and 35a4 so as to penetrate in the stacking direction. Alternatively, pads connected to the via conductors 33p may be arranged on the main surfaces of the insulating layers 35a1, 35a2, 35a3, and 35a4.

[0143] The insulating layers 35a1, 35a2, 35a3, and 35a4 of the via-hole conductors 33p are stacked so as to overlap the insulating layer 31a of the coil conductor 32a and the via-hole conductors 33a. The via-hole conductors 33p are thus connected to form a first connecting conductor 41, which is exposed on the first end surface 11. As a result, the first external electrode 21 and the coil 30 are connected to each other via the first connecting conductor 41.

[0144] As described above, the first connecting conductor 41 preferably connects the first external electrode 21 and the coil 30 in a straight line. The first connecting conductor 41 connects the first external electrode 21 and the coil 30 in a straight line, meaning that the via-hole conductors 33p constituting the first connecting conductor 41 overlap when viewed from above in the stacking direction. The via-hole conductors 33p do not necessarily need to be arranged in a strictly straight line.

[0145] Via conductors 33q are arranged on insulating layers 35b1, 35b2, 35b3, and 35b4, respectively, penetrating in the stacking direction. Pads connected to via conductors 33q may also be arranged on the main surfaces of insulating layers 35b1, 35b2, 35b3, and 35b4.

[0146] The insulating layers 35b1, 35b2, 35b3, and 35b4 of the via-hole conductors 33q, 33q, and 33d are stacked on top of each other, overlapping the insulating layer 31d with the coil conductor 32d and the via-hole conductor 33d. The via-hole conductors 33q are thus connected to form a second connecting conductor 42, which is exposed at the second end surface 12. As a result, the second external electrode 22 and the coil 30 (coil conductor 32d) are connected to each other via the second connecting conductor 42.

[0147] As described above, the second connecting conductor 42 preferably connects the second external electrode 22 and the coil 30 in a straight line. The second connecting conductor 42 connecting the second external electrode 22 and the coil 30 in a straight line means that the via-hole conductors 33q constituting the second connecting conductor 42 overlap with each other when viewed from above in the stacking direction. The via-hole conductors 33q do not necessarily need to be arranged in a strictly straight line.

[0148] When pad portions are connected to the via-hole conductor 33 p constituting the first coupling conductor 41 and the via-hole conductor 33 q constituting the second coupling conductor 42 , the shapes of the first coupling conductor 41 and the second coupling conductor 42 refer to shapes excluding the pad portions.

[0149] Figure 5 and Figure 6 , the case where the number of stacked layers of the coil conductor for forming three turns of the coil 30 is four, that is, the case where the repeated shape is a 3 / 4 turn shape is illustrated, but the number of stacked layers of the coil conductor for forming one turn of the coil is not particularly limited.

[0150] For example, the number of stacked layers of the coil conductor constituting one turn of the coil may be two, that is, the repetitive shape may be a 1 / 2 turn shape.

[0151] The coil conductors forming the coil preferably overlap when viewed from above in the stacking direction. Furthermore, the coil preferably has a circular shape when viewed from above in the stacking direction. Furthermore, if the coil includes a pad portion, the shape other than the pad portion (i.e., the shape of the wire portion) forms the shape of the coil.

[0152] Furthermore, when a pad portion is connected to a via-hole conductor constituting a connecting conductor, the shape of the portion other than the pad portion (ie, the shape of the via-hole conductor) is made to correspond to the shape of the connecting conductor.

[0153] also, Figure 5 The coil conductor shown has a shape in which the repeated pattern forms a circle, but may also have a shape in which the repeated pattern forms a polygon such as a quadrilateral.

[0154] Furthermore, the repetitive shape of the coil conductor may be a 1 / 2 turn shape instead of a 3 / 4 turn shape.

[0155] Preferably in Figure 4 、 Figure 5 and Figure 6 In the laminated coil component having the structure shown above, when the size of the laminated coil component is 0603 size, it is designed as follows in order to further improve the high-frequency characteristics.

[0156] The number of turns of the coil is preferably not less than 36 and not more than 42. When the number of turns is within this range, the total electrostatic capacitance between the coil conductors can be reduced, thereby improving high-frequency characteristics.

[0157] In addition, the coil length is preferably not less than 0.41 mm and not more than 0.48 mm.

[0158] The width of the coil conductor is preferably 45 μm or more and 75 μm or less. Figure 4 The dimensions are shown by the double arrow W.

[0159] The thickness of the coil conductor is preferably 3.5 μm or more and 6.0 μm or less. Figure 4 The dimensions are shown by the double arrow T.

[0160] The distance between the coil conductors is preferably 3.0 μm or more and 5.0 μm or less. Figure 4 The dimensions are shown by the double arrow D.

[0161] The diameter of the land portion of the coil conductor is preferably 30 μm or more and 50 μm or less. Figure 6 The dimensions are shown by the double arrow R.

[0162] When the first main surface of the laminate is the mounting surface, the length of the first external electrode and the length of the second external electrode covering the first main surface of the laminate are preferably 0.20 mm or less, and preferably 0.10 mm or more.

[0163] The length of the first external electrode covering the first main surface of the laminate and the length of the second external electrode are Figure 4 The dimensions shown by the double arrows E1 and E2.

[0164] The relative dielectric constant of the insulating layer constituting the laminated coil component is preferably 8.5 or less, preferably 8.0 or less, and may be 6.5 or more.

[0165] The relative dielectric constant of the insulating layer constituting the laminated coil component can be measured as follows.

[0166] A dielectric constant measurement sample was prepared by molding the insulating layer into a specified shape (e.g., a disc). After forming electrodes, the capacitance was measured at a frequency of 1 MHz and a voltage of 1 Vrms. Based on the measured capacitance, the relative dielectric constant was calculated based on the diameter and thickness of the disc-shaped element body.

[0167] The laminated coil component to be mounted in the optical communication module of the present invention is produced, for example, by the following method.

[0168] The following describes an example in which a ferrite material and a non-magnetic material are mixed and used as the material of the insulating layer. However, only one of the ferrite material and the non-magnetic material may be used as the material of the insulating layer.

[0169] <Ferrite Material Manufacturing Process>

[0170] Fe2O3, ZnO, CuO, and NiO are weighed to a predetermined ratio. Each oxide may contain unavoidable impurities. Next, these weighed materials are wet-mixed and then pulverized to produce a slurry. At this point, additives such as Mn3O4, Bi2O3, Co3O4, SiO2, and SnO2 may also be added. The resulting slurry is then dried and then temporarily fired. The temporary firing temperature is, for example, 700°C to 800°C. In this manner, a powdered ferrite material is produced.

[0171] The ferrite material preferably contains: 40 mol% to 49.5 mol% Fe2O3, 2 mol% to 35 mol% ZnO, 6 mol% to 13 mol% CuO, and 10 mol% to 45 mol% NiO.

[0172] <Non-magnetic material production process>

[0173] Weigh the non-magnetic material powder. If using a mixture of borosilicate glass powder and forsterite powder as the non-magnetic material, prepare glass powder containing potassium, boron, silicon, and aluminum at specified ratios as the borosilicate glass. Also prepare forsterite powder.

[0174] Preferably, borosilicate glass contains the following elements in the following proportions: Si converted into SiO2 is greater than 80 weight% and less than 85 weight%, B converted into B2O3 is greater than 10 weight% and less than 25 weight%, alkali metal A converted into A2O is greater than 0.5 weight% and less than 5 weight%, and Al converted into Al2O3 is greater than 0 weight% and less than 5 weight%.

[0175] Green Sheet Production Process

[0176] The ferrite material and non-magnetic material are weighed to a predetermined ratio. These weighed materials are then mixed with an organic binder such as a polyvinyl butyral resin, an organic solvent such as ethanol or toluene, and a plasticizer, followed by pulverization to produce a slurry. The resulting slurry is then formed into a sheet of a predetermined thickness using a doctor blade method, for example, and then punched into a predetermined shape to produce a green sheet.

[0177] The thickness of the green sheet is preferably 20 μm or more and 30 μm or less.

[0178] The volume ratios of the ferrite material and the non-magnetic material are preferably adjusted and mixed so that the volume ratio of the non-magnetic material relative to the total volume of the ferrite material and the non-magnetic material is 50 volume % or more and 80 volume % or less.

[0179] <Conductor Pattern Formation Process>

[0180] First, via holes are formed by irradiating a predetermined portion of a green sheet with laser light.

[0181] Next, a conductive paste such as silver paste is filled into the via holes and applied to the surface of the raw sheet by screen printing or the like. Thus, for the raw sheet, a conductor pattern for the via hole conductor is formed in the via hole, and a conductor pattern for the coil conductor connected to the conductor pattern for the via hole conductor is formed on the surface. In this way, a coil sheet having a conductor pattern for the coil conductor and a conductor pattern for the via hole conductor formed on the raw sheet is produced. For the coil sheet, a plurality of coil sheets are produced, and for each coil sheet, a pattern equivalent to Figure 5 and Figure 6 The coil conductor shown in the figure is used as a conductor pattern and corresponds to Figure 5 and Figure 6 The via-hole conductor shown is a conductor pattern for the via-hole conductor.

[0182] In addition, by filling the via holes with a conductive paste such as silver paste using a screen printing method, a via hole sheet having a conductor pattern for via hole conductors formed on a green sheet is produced separately from the coil sheet. A plurality of via hole sheets are also produced, and each via hole sheet is formed with a pattern equivalent to Figure 5 and Figure 6 The via-hole conductor shown is a conductor pattern for the via-hole conductor.

[0183] <Laminated Block Production Process>

[0184] By pressing the coil sheet and the via hole sheet into the equivalent Figure 5 and Figure 6 After being stacked in the stacking direction in the order of , they are thermally pressed to produce a stacked body block.

[0185] <Laminate / Coil Production Process>

[0186] First, the laminated body block is cut into predetermined sizes using a dicing machine or the like, thereby producing individual patches.

[0187] Next, the individual chips are fired at a temperature of, for example, 900° C. to 920° C., and for a time of, for example, 2 hours to 8 hours.

[0188] By firing the individual chips, the green sheets of coil and via sheets become insulating layers. This results in a laminate composed of multiple insulating layers stacked in the stacking direction (i.e., the longitudinal direction). The laminate contains a ferrite phase and a non-magnetic phase.

[0189] By firing the singulated chips, the coil conductor pattern and the via conductor pattern of the coil sheet become coil conductors and via conductors, respectively. As a result, a coil is produced in which a plurality of coil conductors are stacked in the stacking direction and electrically connected via the via conductors.

[0190] The stacking direction of the insulating layers and the direction of the coil axis of the coil are parallel to the first main surface, which is the mounting surface of the stack, and are parallel along the longitudinal direction.

[0191] By firing the individual patches, the via conductor pattern of the via sheet becomes a via conductor. This results in a first connecting conductor and a second connecting conductor, each formed by stacking and electrically connecting multiple via conductors in the longitudinal direction. The first connecting conductor is exposed from the first end surface of the stack. The second connecting conductor is exposed from the second end surface of the stack.

[0192] The corners and ridges may be rounded by, for example, barrel polishing the laminate.

[0193] External electrode formation process

[0194] First, a conductive paste containing silver and glass frit is applied to the first and second end faces of the laminate. Next, the resulting coatings are fired to form a base electrode layer on the surface of the laminate. More specifically, a base electrode layer is formed that extends partially from the first end face of the laminate to the first principal surface, the second principal surface, the first side surface, and the second side surface. Additionally, a base electrode layer is formed that extends partially from the second end face of the laminate to the first principal surface, the second principal surface, the first side surface, and the second side surface. The firing temperature for each coating is, for example, 800°C to 820°C.

[0195] Thereafter, a nickel film and a gold film are sequentially formed on the surface of each base electrode layer by electroplating or the like.

[0196] In this way, the first external electrode electrically connected to the coil via the first coupling conductor and the second external electrode electrically connected to the coil via the second coupling conductor are formed.

[0197] The laminated coil component was manufactured based on the above. The gold film was located on the outermost layers of the first and second external electrodes of the laminated coil component.

[0198] The optical communication module of the present invention can be obtained by mounting the laminated coil component manufactured according to the above-described procedure on a substrate having pads having a gold layer on the surface.

[0199] The laminated coil component can be mounted on a substrate by applying a solder paste containing gold-tin solder to a pad having a gold layer on its surface, placing an external electrode having a gold coating on its outermost layer in contact with the solder paste, and performing reflow.

[0200] The reflow conditions may be those generally used for bonding using gold-tin solder.

[0201] Furthermore, other electronic components included in the optical communication module can also be mounted simultaneously with the laminated coil component by performing reflow soldering in the same procedure.

Claims

1. An optical communication module comprising: a substrate having a pad with a gold layer on its surface; and a laminated coil component mounted on the substrate, The optical communication module is characterized in that: The laminated coil component comprises: a laminated body formed by laminating a plurality of insulating layers in a laminating direction and having a coil disposed therein; and an external electrode disposed on a surface of the laminated body and electrically connected to the coil. The external electrode comprises: a gold film located on the outermost layer of the external electrode; The gold film of the external electrode is bonded to the gold layer of the pad of the substrate via gold-tin solder. An IC as an electronic component other than the laminated coil component is mounted on the substrate, and the IC is mounted adjacent to the laminated coil component. The optical communication module is used at a frequency above 60 GHz.

2. The optical communication module according to claim 1, wherein In the laminated coil component, The laminate has a first end face and a second end face that are opposite to each other in a longitudinal direction, a first main face and a second main face that are opposite to each other in a height direction perpendicular to the longitudinal direction, and a first side face and a second side face that are opposite to each other in a width direction perpendicular to the longitudinal direction and the height direction. The external electrode includes: a first external electrode extending from at least a portion of the first end surface of the stack to a portion of the first main surface; and a second external electrode extending from at least a portion of the second end surface of the stack to a portion of the first main surface. The first main surface is a mounting surface, The stacking direction of the stacked body and the coil axis of the coil are parallel to the mounting surface.

3. The optical communication module according to claim 1 or 2, wherein: The thickness of the gold film is 0.4 μm or more and 1.2 μm or less.

4. The optical communication module according to claim 1 or 2, wherein: The external electrode includes a nickel film located closer to the laminate than the gold film.

5. The optical communication module according to claim 4, wherein: The nickel film has a thickness of 1.5 μm or more and 4.5 μm or less.

6. The optical communication module according to claim 1 or 2, characterized in that: The external electrode includes a base electrode layer containing silver and in contact with the laminate.

7. The optical communication module according to claim 1 or 2, characterized in that: The insulating layer includes a ferrite phase and a non-magnetic phase made of a material having a lower dielectric constant than that of a ferrite material constituting the ferrite phase.

8. The optical communication module according to claim 7, wherein: The volume ratio of the non-magnetic phase to the total volume of the ferrite phase and the non-magnetic phase is 55 volume % or more and 80 volume % or less.

9. The optical communication module according to claim 7, wherein: The volume ratio of forsterite to the total volume of the non-magnetic phase is 2 volume % or more and 8 volume % or less.

10. The optical communication module according to claim 1 or 2, characterized in that: The insulating layer contains: B is converted into B2O3 and is 4.3 wt% or more and 8.0 wt% or less, Si is converted into SiO2 and is 27.6 wt% or more and 51.4 wt% or less, Mg is 1.1% by weight or more and 2.1% by weight or less in terms of MgO, Fe is converted into Fe2O3 and is 24.7 wt% or more and 43.5 wt% or less, Ni is 3.3 wt% or more and 5.9 wt% or less as converted to NiO, Zn is 7.7% by weight or more and 13.5% by weight or less in terms of ZnO, The content of Cu is 2.0 wt% or more and 3.6 wt% or less in terms of CuO.

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