1. Field of the Invention
The present invention relates to an inductor component to be accommodated in a printed wiring board or mounted on a printed wiring board. The present invention also relates to a method for manufacturing such an inductor component and a printed wiring board.
2. Description of Background Art
In recent years, the number of electronic components to be mounted externally on a printed wiring board has been decreasing as electronic devices are becoming miniaturized and highly functional. For example, Japanese Laid-Open Patent Publication No. 2010-123879 describes a method for forming an inductor element in a printed wiring board. The inductor element is made up of inductor patterns in substantially an annular shape on a planar view and of a magnetic body formed on the inner-circumferential side of the inductor patterns. In Japanese Laid-Open Patent Publication No. 2010-123879, a magnetic body is positioned in the center of inductor patterns so as to enhance inductor characteristics. The entire contents of this publication are incorporated herein by reference.
According to one aspect of the present invention, an inductor device for a printed wiring board has an insulation layer having a first penetrating hole penetrating through the insulation layer, a magnetic core structure including a magnetic material filled in the first penetrating hole through the insulation layer such that the magnetic core structure including a first magnetic body layer formed in the first penetrating hole is formed through the insulation layer, and a conductor layer formed on the insulation layer and having an inductor pattern such that the inductor pattern is surrounding the circumference of the magnetic core structure.
According to another aspect of the present invention, a method for manufacturing an inductor device for a printed wiring board includes forming on a support base an insulation layer having a first penetrating hole penetrating through the insulation layer, forming on the insulation layer a conductor layer having an inductor pattern such that the inductor pattern is surrounding the circumference of the first penetrating hole formed in the insulation layer, filling a magnetic material in the first penetrating hole such that a magnetic core structure including a first magnetic body layer is formed in the first penetrating hole through the insulation layer and the inductor pattern of the conductor layer surrounds the circumference of the magnetic core structure, forming a second magnetic body layer on the inductor pattern and the insulation layer, and removing the support base from the insulation layer.
According to yet another aspect of the present invention, a printed wiring board has a buildup structure formed of insulation layers and conductive layers, and an inductor device accommodated in or mounted on the buildup structure. The inductor device has an insulation layer having a first penetrating hole penetrating through the insulation layer, a magnetic core structure including a magnetic material filled in the first penetrating hole through the insulation layer such that the magnetic core structure having a first magnetic body layer formed in the first penetrating hole is formed through the insulation layer, and a conductor layer formed on the insulation layer and having an inductor pattern such that the inductor pattern is surrounding the circumference of the magnetic core structure.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings.
Through-hole conductor 36 is formed by filling plating film in penetrating hole 31 for forming a through-hole conductor in the insulative base. Penetrating hole 31 is made up of first opening portion (31a) formed on the first-surface side of the insulative base and of second opening portion (31b) formed on the second-surface side. First opening portion (31a) tapers from the first surface toward the second surface, while second opening portion (31b) tapers from the second surface toward the first surface. First opening portion (31a) and second opening portion (31b) are joined in the insulative base.
A first buildup layer is formed on first surface (F) of insulative base 30 and on inductor component 110. The first buildup layer includes insulation layer (50A) formed to cover first surface (F) of insulative base 30 and inductor component 110, conductive layer (upper conductive layer) (58A) on insulation layer (50A), and via conductors (60A) that penetrate through insulation layer (50A) and connect conductive layer (58A) and the first conductive layer or through-hole conductors. Moreover, connection via conductors (60Aa) connecting electrodes (158AD) of the inductor component and conductive layer (58A) are formed in insulation layer (50A). The first buildup layer further includes insulation layer (50C), conductive layer (uppermost conductive layer) (58C) on insulation layer (50C), and via conductors (60C) that penetrate through insulation layer (50C) and connect conductive layer (58C) and conductive layer (58A) or via conductors (60A, 60Aa).
A second buildup layer is formed on second surface (S) of insulative base 30 and on inductor component 110. The second buildup layer includes insulation layer (50B) formed on second surface (S) of insulative base 30 and on the inductor component, conductive layer (58B) on insulation layer (50B), and via conductors (60B) that penetrate through insulation layer (50B) and connect conductive layer (58B) and the second conductive layer or through-hole conductors. The second buildup layer further includes insulation layer (50D), conductive layer (58D) on insulation layer (50D), and via conductors (60D) that penetrate through insulation layer (50D) and connect conductive layer (58B) and conductive layer (58D).
Solder resist layers 70 with openings 71 are formed on the first buildup layer and on the second buildup layer. Top surfaces of conductive layers (58C, 58D) and via conductors (60C, 60D) exposed through openings 71 of solder-resist layers 70 work as pads. Metal films (72, 74) made of Ni/Au, Ni/Pd/Au or the like are formed on the pads, and solder bumps (76U, 76D) are formed on the metal films. An IC chip is mounted on the printed wiring board through solder bumps (76U), and the printed wiring board is mounted on a motherboard through solder bumps (76D).
In printed wiring board 10 of the first embodiment, inductor component 110 is accommodated in penetrating hole 20 of insulative base 30. Filler 50 is filled in penetrating hole 20. Filler 50 is filled in the space between side walls of opening 20 (side walls in the insulative base exposed by opening 20) and inductor component 110. Accordingly, inductor component 110 is secured inside penetrating hole 20.
Here, insulation layers (50A, 50B) formed on both surfaces of insulative base 30 contain core material such as glass cloth, and insulation layers (50C, 50D) positioned on their respective external sides of insulation layers (50A, 50B) do not contain core material. By employing insulation layers (50A, 50B) with core material, warping caused by thermal history while buildup layers are formed, for example, is suppressed.
In the first embodiment, an inductor component is built into the insulative base, allowing the inductor component to be built into a printed wiring board without increasing the number of insulation layers. Even when an inductor component formed by alternately laminating multiple inductor patterns and resin insulation layers is built into a printed wiring board, the number of insulation layers on the insulative base (interlayer resin insulation layers in the first or second buildup layer) does not increase in the first embodiment. The thickness of an insulative base is usually greater than the thickness of insulation layers on the insulative base. Thus, in the first embodiment, an inductor component with a greater number of inductor patterns can be built into a printed wiring board without increasing the number of insulation layers on the insulative base. An inductor component with high inductance is built into a thin printed wiring board. In the first embodiment, increasing the number of conductive layers of the buildup layers is not required to enhance the inductance of an inductor formed in a printed wiring board. If multiple inductor patterns are formed in a buildup layer, they would increase the difference in the amount of conductors on the first-surface side and second-surface side of the insulative base, and warping is more likely to occur. However, in the first embodiment, since no inductor pattern is formed in the first buildup layer or the second buildup layer, the difference in the amount of conductors decreases on the first-surface side and second-surface side of the insulative base. As a result, warping in the printed wiring board is small.
Part of first inductor pattern (158A) works as electrode (158AD). Connection via conductor (160C) is formed on electrode (158AD). The inductor component of the first embodiment has resin insulation layers and inductor patterns laminated alternately, and inductor patterns on different layers are connected by via conductors in resin insulation layers. The inductor component of the first embodiment includes multiple laminated coils (CA, CB), and those laminated coils are each connected parallel or in series. The inductor component in
In resin insulation layers (150C, 150E, 150G) sandwiched by inductor patterns, penetrating hole 170 is formed to be concentric to the inductor patterns, and columnar first magnetic body layer 172 is filled in the penetrating hole. Also, second magnetic body layer 174 covers inductor pattern (158G). First magnetic body layer 172 and second magnetic body layer 174 are made of the same material, using resin containing magnetic particles of iron-nickel alloy, iron alloy, amorphous alloy or the like. The amount of magnetic particles is 30˜60 vol. %. First magnetic body layer 172 made of resin with magnetic particles mixed in is positioned in the center of inductor patterns, and second magnetic body layer 174 is positioned on the outer side of inductor pattern (158G). By so setting, the magnetic permeability is enhanced. Accordingly, desired inductance is achieved using a thin inductor component with fewer layers, thus reducing the thickness of a printed wiring board with the inductor component built into the insulative base.
In the first embodiment, a first magnetic body layer (magnetic core) is formed in the vicinity of the center of the inductor to achieve higher inductance with fewer coils.
Moreover, by forming a magnetic body layer on the outermost inductor pattern of the inductor component, magnetic flux in the inductor component seldom leaks outside. To prevent a reduction of inductance values or lowered Q factor, regions without conductive circuits are not required to be formed directly on or directly under the inductor component. Volumes of conductive circuits in the first and second buildup layers seldom become unbalanced. A printed wiring board with smaller warping is provided.
Meanwhile, the output from the adjacent laminated coil is connected to first inductor pattern (158G1) from input pad (158GDI) (
The fourth inductor pattern (uppermost inductor pattern) is formed with a wiring pattern in a semicircular coil shape. Inductor patterns except for the lowermost inductor pattern are made up of two wiring patterns. In the first embodiment, a laminated coil is connected through connection wiring (L10) to its adjacent laminated coil having the same shape. Inductor component 110 of the first embodiment is formed with two laminated coils.
When an inductor component includes multiple laminated inductors, the inductor component may include a common output electrode to share. In such a case, laminated inductors are connected to each other in parallel. A connection via conductor may be formed on each output electrode of the laminated coils. In such a case, each laminated coil is connected to a connection terminal through a connection circuit in a buildup layer. Multiple laminated coils are connected in the buildup layer. When multiple laminated coils are connected in parallel, multiple laminated coils are connected at low resistance. Thus, a low-resistance inductor component is obtained even if the inductor component is formed with multiple laminated coils.
The inductor component shown in
The inductor component may be coated with resin film containing inorganic particles. Resin film is not magnetic. In addition to particles, resin film or coating film contains resin such as epoxy. Thus, bonding strength between the inductor component and resin filler is enhanced, preventing defects such as disconnection in conductive layers of a printed wiring board caused when peeling occurs between the inductor component and resin filler. Other than magnetic particles, coating film may also contain inorganic particles that are not magnetic. Silica particles and alumina particles are examples of inorganic particles that are not magnetic. The thermal expansion coefficient of the coating film is reduced.
The inductor component is formed with resin insulation layers and inductor patterns laminated alternately, and has electrodes to be connected to connection via conductors of the printed wiring board. Thus, the thickness of the inductor component is adjustable by adjusting the number of resin insulation layers and the number of inductor patterns. Therefore, the inductor component is manufactured by considering the thickness of the insulative base. Then, the inductance value is adjusted by the number of inductor patterns and the number of laminated inductors. Therefore, the inductor component of an embodiment of the present invention is suitable for a component to be built into the insulative base. Also, since the printed wiring board and the inductor component are connected by connection via conductors, the inductor component of an embodiment of the present invention is suitable for a component to be built into a printed wiring board. The inductor component may be covered by resin film that is not magnetic. Deterioration of the inductor component is suppressed.
In the embodiment, buildup layers and the inductor component are manufactured by technology used in the technological field of printed wiring boards. Since buildup layers and the inductor component are manufactured separately, the thickness of inductor wiring patterns may be set greater than the thickness of the conductive layers of buildup layers. Thus, a low-resistance inductor component is built into a printed wiring board, and a printed wiring board with fine conductive circuits is obtained. The thickness of inductor wiring patterns is preferred to be 1.2˜3 times the thickness of the conductive layers of buildup layers. An inductor component with low resistance and high inductance is obtained. A thin printed wiring board with fine circuits is obtained.
In addition, the surface of each inductor pattern may be roughened. In such a case, adhesiveness with resin insulation layers and magnetic body layers improves. Moreover, the inner wall of penetrating hole 170 may also be roughened. In such a case, adhesiveness improves between the magnetic body layer filled in penetrating hole 170 and resin insulation layers.
(A) Preparing Resin-Containing Solution
In a mixed solvent containing 6.8 grams of MEK and 27.2 grams of xylene, 85 grams of epoxy resin (brand name: Epikote 1007, made by Japan Epoxy Resin Co., Ltd.) and magnetic particles of iron (III) oxide or the like are added. Examples of magnetic particles are chromium ferrite (ferrichrome), cobalt ferrite, barium ferrite and the like.
(B) Forming Magnetic-Material Solution
Dicyanamide as a curing agent (brand name: CG-1200, made by BTI Japan) and a curing catalyst (brand name: Curezol 2E4HZ, made by Shikoku Chemical Corporation) are added to the resin-containing solution prepared in (A) above. Then, the mixture is blended using a three-roll mill to form a magnetic-material solution. The amounts of the curing agent and curing catalyst are each 3.3 grams based on 100 grams of epoxy. The magnetic-material solution is applied on a polyethylene terephthalate sheet using a roll coater (made by Cermatronics Boeki Co., Ltd.). Then, the solution is heated and dried under conditions of 160° C. for 5 minutes to remove the solvent. Film for magnetic body layers containing magnetic particles is obtained. The thickness is approximately 20 μm˜50 μm. The amount of magnetic particles in the magnetic-material solution and film for magnetic body layers is 30 vol. %˜60 vol. %.
Commercially available double-sided copper-clad laminate (130Z) and copper foils (134A, 134B) are prepared, and the copper foils are laminated on both surfaces of the double-sided copper-clad laminate. The peripheries of copper foils and peripheries of double-sided copper-clad laminate (130Z) as a support sheet are bonded using ultrasound (
Resin insulation layers of the first embodiment contain a resin that is relatively soluble in a roughening solution and a resin that is relatively insoluble. Resins relatively soluble in a roughening solution are, for example, thermoplastic resins such as polyethylene resin, polypropylene resin, polyester resin, polystyrene resin, acrylic resin, polyamide and polyethylene terephthalate. Resins relatively insoluble in a roughening solution are epoxy-based resins described above.
Electroless plated films (152C, 152D) are formed on resin insulation layers (150C, 150D) (
Using a laser, for example, penetrating holes 170, which are to be concentric to their respective inductor patterns, are formed in resin insulation layers (150G, 150E, 150C) and resin insulation layers (150H, 150F, 150D) (
Using a router or the like, the laminate is cut along lines (X1, X1) inside bonding portions (136A, 136B) as shown in
(1) The starting material is double-sided copper-clad laminate (30Z) having insulative base (30A) and copper foils 32 laminated on both of its surfaces. The thickness of the insulative base is 100˜400 μm. If the thickness is less than 100 pm, the substrate strength is too low. If the thickness exceeds 400 pm, the thickness of the printed wiring board is too thick. The insulative base has first surface (F) and second surface (S) opposite the first surface. Black-oxide treatment not shown in the drawing is conducted on surfaces of copper foils 32 (
(2) A laser is irradiated on double-sided copper-clad laminate (30Z) from the first-surface (F) side of the insulative base. First opening portions (31a) are formed, becoming narrower from the first surface of the insulative base toward the second surface (
(3) A laser is irradiated on double-sided copper-clad laminate (30Z) from the second-surface (S) side of the insulative base. Second opening portions (31b) are formed, becoming narrower from the second surface of the insulative base toward the first surface (
(4) Electroless plating is performed to form electroless plated film 33 on the inner walls of penetrating holes 31 and on copper foils 32 (
(5) Electrolytic plating is performed to form electrolytic plated film 37 on electroless plated film 33. Through-hole conductors 36 are formed in the penetrating holes. Through-hole conductors 36 are made up of electroless plated film 33 on the inner wall of the penetrating hole and electrolytic plated film 37 filled in the penetrating holes (
(6) Etching resist 35 with a predetermined pattern is formed on electrolytic plated film 37 on surfaces of insulative base 30 (
(7) Electrolytic plated film 37, electroless plated film 33 and copper foil 32 exposed from the etching resist are removed. Then, the etching resist is removed so that conductive layers (34A, 34B) and through-hole conductors 36 are formed (
(8) Opening 20 to accommodate an inductor component is formed by a drill in the center of insulative base (30A). Accordingly, the insulative base is completed (
(9) Tape 94 is laminated on second surface (S) of insulative base 30. Opening 20 is covered by the tape (
(10) Inductor component 110 is placed on tape 94 exposed through opening 20 (
(11) B-stage prepreg is laminated on first surface (F) of insulative base 30. Resin comes out of the prepreg into the opening by thermal pressing, and opening 20 is filled with filler (resin filler) 50 (
(12) After the tape is removed (FIG. 11(A)), B-stage prepreg is laminated on second surface (S) of insulative base 30. Prepreg on the first and second surfaces of the insulative base is cured. Insulation layers (interlayer resin insulation layers) (50A, 50B) are formed on the first and second surfaces of the insulative base (
(13) By irradiating a CO2 gas laser from the first-surface side, openings (51A) for connection via conductors are formed in insulation layer (50A) to reach electrodes (158AD) of inductor component 110. At the same time, via-conductor openings 51 reaching conductive layer (34A) or through-hole conductors 36 are also formed. From the second-surface side, via-conductor openings 51 reaching conductive layer (34B) or through-hole conductors 36 are formed in insulation layer (50B) (
(14) Electroless plating is performed to form electroless plated film 52 on the inner walls of via-conductor openings and on the insulation layers (
(15) Plating resist 54 is formed on electroless plated film 52 (
(16) Next, electrolytic plating is performed to form electrolytic plated film 56 on the electroless plated film exposed from the plating resist (
(17) Next, plating resist 54 is removed using a 5% NaOH solution. Then, electroless plated film 52 exposed from the electrolytic copper-plated film is etched away so that conductive layers (58A, 58B) made of electroless plated film 52 and electrolytic plated film 56 are formed. Conductive layers (58A, 58B) include multiple conductive circuits and lands of via conductors. Simultaneously, via conductors (60A, 60B) and connection via conductors (60Aa) are formed (
(18) Procedures shown in
(19) Solder-resist layer 70 having openings 71 is formed on first and second buildup layers (
(20) Metal film made of nickel layer 72 and gold layer 74 on nickel layer 72 is formed on the pads (
(21) Next, solder bumps (76U) are formed on the pads of the first buildup layer, and solder bumps (76D) are formed on the pads of the second buildup layer. Printed wiring board 10 with solder bumps is completed (
Penetrating hole 170 is formed in resin insulation layers (150Z, 150A, 150C, 150E) to be concentric to the inductor patterns. Columnar first magnetic body layer 172 is filled in the penetrating hole. Second magnetic body layer (174A) covers inductor pattern (158G) on resin insulation layer (150E). Opening (174a) of second magnetic body layer (174A) exposes terminal (158GD). Second magnetic body layer (174B) covers the lower-surface side of resin insulation layer (150Z). First magnetic body layer 172 and second magnetic body layers (174A, 174B) are made of the same material as that of the first embodiment.
In inductor component 110 of the second embodiment, by positioning first magnetic body layer 172 made of resin containing magnetic particles in the center of inductor patterns, and by forming second magnetic body layers (174A, 174B) on both surfaces, magnetic permeability is enhanced. Accordingly, desired inductance is achieved by a thin inductor component with fewer layers. Thus, a printed wiring board with the inductor component built into its insulative base is made thinner.
By providing magnetic body layers to cover inductor patterns on the outermost layers, magnetic flux is blocked and seldom leaks to the outside from inductor component 110 of the second embodiment. As a result, it is easier to secure desired inductor characteristics.
Using a laser or a drill, penetrating hole 170 is formed in resin insulation layers (150E, 150C, 150A, 150Z) to be concentric to each inductor pattern (
Magnetic-layer film the same as in the first embodiment is laminated on inductor pattern (158G), and second insulative layer (174A) with openings (174a) is formed on inductor pattern (158G) (
In the first and second embodiments, an inductor component was built into the insulative base of a printed wiring board. In the third embodiment, inductor 210 is formed in a first-surface (F) side buildup layer of the insulative base. Inductor 210 is made up of inductor pattern (58C) formed on interlayer resin insulation layer (50B), inductor pattern (158C) formed on interlayer resin insulation layer (150B), inductor pattern (258C) formed on interlayer resin insulation layer (250B) and via conductors (60B, 160B, 260B) connecting inductor patterns (58C, 158C, 258C), first magnetic body layer 272 filled in penetrating hole 270 formed in interlayer resin insulation layers (150B, 250B), and magnetic-material film 274 coating inductor pattern (258C).
In the third embodiment, the following buildup layers are laminated on insulative base 30 as shown in
As shown in
As shown in
As shown in
As shown in
In inductor component 210 of the fourth embodiment, second penetrating holes (170C, 170D) are formed in the outer circumferential-side region of inductor patterns where no inductor is formed. Third magnetic body layers (172C, 172D) are filled in second penetrating holes (170C, 170D). Second penetrating holes (170C, 170D) are formed in an arc shape when seen in a lateral cross section.
In the fourth embodiment, magnetic body layers are also formed in regions where no inductor is formed. By so setting, it is easier to block magnetic flux toward side directions of the inductor and to secure desired inductor characteristics.
Regarding the method for manufacturing an inductor component according to the fourth embodiment, resin insulation layers (150A, 150C, 150E) and inductor patterns (158A, 158C, 158E, 158G) are formed the same as in the first embodiment (FIG. 21(A)), and then, first penetrating hole 170 is formed in the center of inductor patterns of the laminate, and second penetrating holes (170C, 170D) are formed in the outer circumferential-side region of the inductor patterns where no inductor is formed (
According to an embodiment of the present invention, an inductor component is accommodated in or mounted on a printed wiring board and includes an insulation layer having a first penetrating hole, a first magnetic body layer formed in the first penetrating hole, and an inductor pattern formed on the insulation layer and on at least part of the circumferential portion of the first magnetic body layer.
In the inductor component according to an embodiment of the present invention, the magnetic permeability increases by forming a magnetic body layer in the shaft center of inductor patterns. Thus, desired inductor characteristics are achieved without increasing the number of inductor-pattern layers. Moreover, an inductor component of the present invention can be manufactured by a simplified process such as forming a penetrating hole in an insulation layer and forming a magnetic body layer in the penetrating hole.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
Number | Date | Country | Kind |
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2012-143230 | Jun 2012 | JP | national |
The present application is a continuation of and claims the benefit of priority to U.S. application Ser. No. 13/927,243, filed Jun. 26, 2013, which is based upon and claims the benefit of priority to Japanese Patent Application No. 2012-143230, filed Jun. 26, 2012. The entire contents of these applications are incorporated herein by reference.
Number | Date | Country | |
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Parent | 13927243 | Jun 2013 | US |
Child | 14603822 | US |