JP2008288225A - Capacitor and manufacturing method thereof, and substrate with built-in capacitor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor that does not adversely affect the characteristics of a dielectric layer even if forming a through hole or plating the through hole, to provide a method for manufacturing the capacitor, to provide a substrate incorporating the capacitor, and to provide a method of manufacturing the substrate incorporating the capacitor. <P>SOLUTION: The capacitor 100 has: a dielectric layer 10; a first capacitive electrode 21 formed on one main surface of the dielectric layer; and a second capacitive electrode 22 formed on the other main surface of the dielectric layer. The dielectric layer has a through conductor from one main surface to the other main surface, and a through hole is formed inside the through conductor. The substrate incorporating a capacitor has a substrate body having a wiring conductor, and the capacitor 100. In this case, the through conductor is connected to the wiring conductor electrically by a connection conductor formed inside the through hole. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a capacitor, a capacitor built-in substrate in which the capacitor is built, and a manufacturing method thereof.

  Capacitors are used as electronic components for electronic devices. Capacitors are required to be miniaturized as electronic devices are miniaturized. However, in recent years, capacitors can be embedded in a mounting board for further miniaturization. Has been done.

  The embedding of the capacitor in the mounting board has not only the advantage of reducing the size of the electronic device, but also the advantage that the inductance is reduced by shortening the circuit length, particularly in an electronic device using a high-frequency signal. Since it is important to reduce the inductance, there is a strong demand for embedding the capacitor in the mounting board from this viewpoint.

Examples of a capacitor suitable for embedding in a mounting substrate and a mounting substrate in which the capacitor is embedded include a capacitor and a mounting substrate described in Patent Document 1. The capacitor described in Patent Document 1 is formed by forming a dielectric layer on a metal foil by a MOD method (organometallic decomposition method) or a sputtering method, and forming a conductive layer on the dielectric layer by a sputtering method (patent) FIG. 11 of Reference 1). In the printed wiring board described in FIG. 14 of Patent Document 1, the capacitor is embedded in the substrate, and the circuit of the substrate and the electrode of the capacitor are connected by a circuit conductor formed so as to penetrate the capacitor in the thickness direction. ing. The circuit conductor is described as being a “plated microvia”.
JP-A-2005-39282 (particularly, paragraphs [0063] to [0072], FIGS. 11 to 15)

  The invention described in Patent Document 1 has the following problems.

  That is, first, in the capacitor described in Patent Document 1, the dielectric layer is formed by a thin film process such as a MOD method or a sputtering method. When the dielectric layer is formed by a thin film process, there is a problem that the film formation cost is relatively high. Furthermore, since the dielectric layer is formed by a thin film process on the metal foil having a smooth surface, it is difficult to obtain sufficient adhesion strength between the metal foil and the dielectric layer, and due to the stress received when embedding the capacitor in the substrate, The interface between the metal foil and the dielectric layer may be peeled off.

  Secondly, so-called via holes are used to connect the electrodes of the capacitor and the circuit on the printed wiring board, but there is a problem that the formation of the via holes adversely affects the characteristics of the dielectric layer. More specifically, the via hole is formed by forming a through hole with a laser or the like and then filling the inside of the through hole with a conductor by plating or the like. The via hole is formed by the heat of the laser beam when the through hole is formed. The characteristics of the body layer may be adversely affected, and also when the conductor is filled by plating, the plating solution comes into contact with the dielectric layer, thereby adversely affecting the characteristics of the dielectric layer.

  The present invention has been made in view of such problems, and the interface between the electrode and the dielectric layer has sufficient adhesion strength, and even if a through-hole is formed or plated on the through-hole, the dielectric is provided. It is an object of the present invention to provide a capacitor that does not adversely affect the characteristics of the body layer and a method for manufacturing the same, and to provide a capacitor built-in substrate that includes such a capacitor and a method for manufacturing the same.

  In order to solve the above problems, a capacitor according to the present invention includes a dielectric layer, a first capacitor electrode formed on one main surface of the dielectric layer, and the other main surface of the dielectric layer. The dielectric layer has a through conductor extending from one main surface to the other main surface, and a through hole is formed inside the through conductor. Features.

  As described above, in the capacitor of the present invention, since the through hole is formed inside the through conductor, heat and mechanical shock during formation of the through hole do not directly reach the dielectric layer, and the dielectric layer There is no risk of adversely affecting properties. Also, when this capacitor is mounted on the substrate, the connection conductor necessary for connection with the wiring of the substrate may be formed inside the through hole. For example, even when the connection conductor is formed by wet plating. The plating solution does not directly touch the dielectric layer, and there is no possibility of adversely affecting the characteristics of the dielectric layer.

  Furthermore, the capacitor of the present invention is characterized in that the dielectric layer, the first and second capacitive electrodes, and the through conductor are sintered simultaneously.

  Thereby, while being cheaper than the capacitor manufactured by the thin film method, the dielectric layer and the conductor (the first and second capacitance electrodes and the through conductor) are fired at the same time, so that the dielectric layer and the conductor The bonding strength at the interface increases, and the possibility of peeling at the interface can be reduced even when stress is applied during or after mounting the substrate.

  A capacitor-embedded substrate according to the present invention includes a substrate body having a wiring conductor and the capacitor according to claim 1 or 2, and the through conductor and the capacitor are formed by a connection conductor formed in the through hole. The wiring conductor is electrically connected.

  As a result, since the connection conductor that electrically connects the capacitor and the wiring conductor is formed inside the through hole and does not directly touch the dielectric layer, for example, even when the connection conductor is formed by wet plating There is no possibility that the plating solution contacts the dielectric layer and adversely affects the characteristics of the dielectric layer.

  The method of manufacturing a capacitor according to the present invention includes a step of preparing a dielectric green sheet including a dielectric powder and a binder and having a through hole, and a conductor green sheet including a metal powder and a binder, A step of forming a laminate by stacking and crimping the conductor green sheet on both main surfaces of the dielectric green sheet so as to cover at least a part of the through hole; and firing the laminate, The method includes a step of obtaining a fired body having a through conductor in which a part of the conductor green sheet is filled inside the through hole, and a step of forming a through hole penetrating the through conductor.

  As a result, a through-hole is formed inside the through-conductor, so that heat and mechanical shock during the formation of the through-hole do not directly reach the dielectric layer, which may adversely affect the characteristics of the dielectric layer. Absent. Even when the capacitor is mounted on the substrate, the connection conductor necessary for connection to the wiring of the substrate may be formed inside the through hole. For example, even when the connection conductor is formed by wet plating. The plating solution does not directly touch the dielectric layer, and there is no possibility of adversely affecting the characteristics of the dielectric layer.

  In addition, since the dielectric green sheet and the conductor green sheet are manufactured by laminating and firing, it can be manufactured at a lower cost than a capacitor by a thin film process, and the interface between the dielectric layer and the conductor layer can be manufactured. Bonding strength is increased, and peeling of the interface can be prevented.

  The method for manufacturing a capacitor-embedded substrate according to the present invention includes a step of preparing a substrate body having a wiring conductor, a step of placing the capacitor according to claim 1 or 2 on the substrate body, and the through hole. Forming a connection conductor in the inside, and electrically connecting the through conductor and the wiring conductor by the connection conductor.

  Since the connection conductor is formed in the through hole formed inside the through conductor, for example, even when the connection conductor is formed by wet plating, the plating solution does not directly contact the dielectric layer. Therefore, there is no possibility of adversely affecting the characteristics of the dielectric layer.

  The method for manufacturing a capacitor-embedded substrate according to the present invention includes a dielectric green sheet including dielectric powder and a binder and having a through hole, and a conductor green sheet including a metal powder and a binder. A step of forming a laminate by stacking and crimping the conductor green sheet on both main surfaces of the dielectric green sheet so as to cover at least a part of the through-hole, and firing the laminate Then, obtaining a fired body having a through conductor formed by filling a part of the conductor green sheet inside the through hole, and placing the fired body on a substrate body having a wiring conductor; Forming a through hole penetrating at least the through conductor; forming a connection conductor in the through hole; and electrically connecting the through conductor and the wiring conductor by the connection conductor. And having the steps of, a.

  As a result, a through-hole is formed inside the through-conductor, so that heat and mechanical shock during the formation of the through-hole do not directly reach the dielectric layer, which may adversely affect the characteristics of the dielectric layer. Absent. In addition, since the through conductor of the capacitor and the wiring conductor of the substrate body are electrically connected by a connection conductor formed inside the through hole, for example, when the connection conductor is formed by wet plating, the plating solution is directly There is no risk of adversely affecting the characteristics of the dielectric layer without touching the dielectric layer.

  In the present invention, the method for forming the connection conductor is not limited to the wet plating method. For example, the connection conductor may be formed by filling with a conductive paste, but when the connection conductor is formed by the wet plating method. In addition, the present invention is more effective.

  As described above, according to the present invention, the through conductor that penetrates the dielectric layer is provided in the capacitor, and the through hole is formed inside the through conductor. Since the mechanical shock does not directly reach the dielectric layer, and a via hole necessary for electrical connection with the substrate body may be formed inside the through hole, the plating solution directly touches the dielectric layer. There is no. Therefore, the characteristics of the dielectric layer are not adversely affected when the through hole is formed or when it is electrically connected to the substrate body. In addition, since the dielectric green sheet and the conductor green sheet are laminated and fired at the same time, it can be manufactured at a lower cost than a capacitor by a thin film process, and the interface between the dielectric layer and the conductor layer. The bonding strength of the film becomes strong, and the peeling of the interface can be prevented.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1A is a plan view showing a capacitor according to the present invention, and FIG. 1B is a cross-sectional view taken along the line AA in FIG.

  The capacitor 100 according to the present invention includes a dielectric layer 10, a first capacitive electrode 21 and a first electrode pad 31 formed on one main surface of the dielectric layer 10, and the other main layer of the dielectric layer 10. The second capacitor electrode 22 and the second electrode pad 32 formed on the surface, and the through conductor 11 penetrating the dielectric layer 10 in the thickness direction are provided.

  The first electrode pad 31 is electrically insulated from the first capacitor electrode 21 and is electrically connected to the second capacitor electrode 22 through the through conductor 11. The through conductor 11 is formed integrally with the first electrode pad 31 and the second capacitor electrode 22.

  The second electrode pad 32 is electrically insulated from the second capacitor electrode 22 and is electrically connected to the first capacitor electrode 21 through the through conductor 11. The through conductor 11 is formed integrally with the second electrode pad 32 and the second capacitor electrode 22.

  A through hole 12 is formed in a substantially central portion of the through conductor 11 so as to penetrate between both main surfaces of the capacitor 100.

  FIG. 2 is a sectional view showing a capacitor built-in substrate according to the present invention. The capacitor built-in substrate according to the present invention includes a substrate body 200 and the capacitor 100 shown in FIG.

  Capacitor 100 is bonded to the upper surface of substrate body 200 by cured resin 210. The cured resin 210 is also formed on the upper surface side of the capacitor 100, and the capacitor 100 is embedded in the cured resin 210. A wiring conductor 201 is formed on the upper surface and inside of the substrate body 200, and the through conductor 11 and the wiring conductor 201 are electrically connected by a connection conductor 202 formed in the through hole 12 of the capacitor 100. .

  Next, a method for manufacturing a capacitor and a capacitor built-in substrate according to the present invention will be described with reference to FIGS.

(1) Step of preparing a green sheet Ratio of dielectric ceramic powder having an average particle diameter of 0.2 mm mainly composed of BaTiO ₃ , binder mainly composed of polyvinyl butyral, toluene and ethanol in a volume ratio of 1: 1 A dielectric ceramic slurry was prepared by mixing and dispersing with the solvent mixed in. The mixing ratio of the dielectric ceramic powder, the binder and the solvent was 10:10:80 by volume. The volume of the dielectric powder was calculated by measuring the weight and dividing by the theoretical density (hereinafter, the volume of the powder was calculated in the same manner). Next, a dielectric ceramic slurry was formed into a sheet by a doctor blade method to obtain a dielectric green sheet having a thickness of 2 μm.

  Then, as shown in FIG. 3A, a through hole 42 having a diameter of 200 μm was formed in the dielectric green sheet 41 by laser processing.

  Moreover, Ni powder with an average particle size of 0.5 μm, a binder mainly composed of polyvinyl butyral, and a solvent in which toluene and ethanol were mixed at a volume ratio of 1: 1 were mixed and dispersed to prepare a conductor slurry. . The mixing ratio of Ni powder, binder, and solvent was 10:10:80 by volume. Next, the conductor slurry was formed into a sheet by a doctor blade method to obtain a conductor green sheet having a thickness of 9 μm.

Furthermore, Al ₂ O ₃ powder having an average particle diameter of 1.0 μm is prepared, and a binder mainly composed of polyvinyl butyral and a solvent in which toluene and ethanol are mixed at a volume ratio of 1: 1 are mixed and dispersed. A ceramic slurry for assisting firing was prepared. The mixing ratio of Al ₂ O ₃ powder, binder and solvent was 10:10:80 by volume ratio. Next, the ceramic slurry for baking assistance was shape | molded by the doctor blade method in the sheet form, and the 100-micrometer-thick green sheet for baking assistance was obtained.

(2) Lamination process Next, the dielectric green sheet 41, the conductor green sheet 43, and the firing auxiliary green sheet 44 were laminated and pressed in a positional relationship as shown in FIG. More specifically, the firing green sheet 44 is disposed so that the conductor green sheets 43 are in contact with both main surfaces of the dielectric green sheet 41 and sandwich the outside of the conductor green sheet 43. At this time, the conductor green sheet 43 is filled in the through hole 42 by pressure bonding, and the through conductor 11 is formed. Even if the conductor green sheet 43 is not sufficiently filled in the through-hole 42 at the time of crimping, the viscosity of the conductor green sheet 43 decreases during firing, which will be described later, and the conductor green sheet 43 is filled in the through-hole 42. Is done.

(3) Firing step The obtained laminate was degreased by heat treatment at 280 ° C. for 5 hours in a nitrogen atmosphere. Further, it was heated to 1150 ° C. in a reducing atmosphere, kept for 2 hours, and then cooled in a neutral atmosphere. The firing atmosphere is based on the oxidation-reduction equilibrium oxygen partial pressure of Ni, and the state where the oxygen partial pressure is lower than this is called the reduction atmosphere, the oxygen partial pressure equal to the equilibrium oxygen partial pressure and the vicinity thereof are called the neutral atmosphere. .

  By firing, a sintered body 50 including the dielectric layer 10, the first and second conductor layers 51 and 52, and the through conductor 11 was obtained as shown in FIG. The thickness of the dielectric layer 10 was 1.2 μm, and the total thickness of the first and second conductor layers 51 and 52 was 15 μm.

  During firing, the firing auxiliary green sheet 44 was naturally peeled from the conductor green sheet 43. This is because stress is generated at the interface due to the difference in shrinkage behavior during firing between the conductor green sheet 43 and the firing auxiliary green sheet 44.

(4) Conductor layer patterning step A resist is applied on the first conductor layer 51, exposed and developed to be patterned into a predetermined shape, and part of the first conductor layer is removed by wet etching. Thus, a groove 53 was formed, and the first conductor layer 53 was divided into the first capacitor electrode 21 and the first electrode pad 31 as shown in FIG. Similarly, the second conductor layer 54 was patterned and divided into the second capacitor electrode 22 and the second electrode pad 32.

(5) Through-hole formation process The through-hole 12 with a diameter of 100 micrometers was formed by laser processing so that it might become concentric with the through-conductor 11 with a diameter of 200 micrometers (FIG.3 (e)). As the laser, THG-YAG, which is easy to process metal, was used, but the laser is not limited to this. By forming the through hole 12, the capacitor 100 according to the present invention was completed.

  Here, the terminals were brought into contact with the first and second capacitor electrodes 21 and 22, and a voltage of 1 V was applied to measure the insulation resistance value. When the insulation resistance of 10 samples was measured, the resistance values of all the samples showed a value of 1 GΩ or more, and it was confirmed that the samples had sufficient insulation properties.

(6) Mounting process on substrate body Next, a substrate body 200 made of a build-up epoxy substrate having wiring conductors 201 on the upper surface and inside is prepared, and an uncured epoxy film having a thickness of 50 μm is pasted on the substrate body 200. And a capacitor 100 is placed thereon. Further, an uncured epoxy film was stuck on the capacitor 100 and then cured at a predetermined temperature to obtain a cured resin 210. As a result, the capacitor 100 was fixed on the substrate body 200.

(7) Step of forming connection conductor Next, a through hole 203 having a diameter of 100 μm was formed up to the wiring conductor 201 of the substrate body 200 by a CO ₂ laser so as to coincide with the through hole 12 formed in the capacitor 100 (FIG. 4 (b)). A catalyst was applied to the inner wall of the through hole 203 to form a Cu film by electroless plating, and further, electrolytic plating was performed to fill the through hole 203 with Cu to form a connection conductor 202. As a result, the substrate with a built-in capacitor according to the present invention was completed as shown in FIG.

  A terminal is brought into contact with the connection conductor 202 electrically connected to the first capacitor electrode 21 of the capacitor 100 and the connection conductor 202 connected to the second capacitor electrode 22, and a voltage of 1 V is applied. When the insulation resistance was measured, the resistance value exceeded 1 GΩ in all 10 samples, and it was confirmed that a sufficient insulation resistance value was obtained.

Comparative example

  In order to compare with the present invention, a capacitor was manufactured by the following method.

  A dielectric green sheet, a conductor green sheet, and a firing auxiliary green sheet were prepared by the same method as in (1) above. However, no through hole was formed in the dielectric green sheet.

  Next, the dielectric green sheet 41, the conductor green sheet 43, and the firing auxiliary green sheet 44 are laminated and pressure-bonded as shown in FIG. 5A, and fired under the same conditions as in the above (3) to obtain a sintered body. It was.

  Next, after patterning the first and second conductor layers 51 and 52 as shown in FIG. 5B by the same method as the above (4), the through-hole 12 was formed with a THG-YAG laser ( FIG. 5 (c)). At this time, since no through conductor was formed in this comparative example, the laser punched the dielectric layer 10.

  Here, when the terminal was brought into contact with the first and second conductor layers 51 and 52 and a resistance value was measured by applying a voltage of 1 V, the lowest value among the 10 samples was 85Ω, the highest value was 960Ω, the average The value was 310Ω, which was significantly lower than that of the present invention. This is because when the laser punches out the dielectric layer, the dielectric layer is rapidly exposed to high temperatures and cracks occur, resulting in a decrease in insulation, or the dielectric is melted by the heat of the laser to become a conductor. Is the cause.

  Next, a second embodiment of the present invention will be described. Description of parts common to the first embodiment will be omitted as appropriate.

  First, the sintered compact 50 shown to Fig.6 (a) is obtained by the same method as (1)-(4) of Example 1. FIG. This sintered body 50 is the same as the sintered body 50 shown in FIG. Next, the sintered body 50 is fixed on the substrate body 200 as shown in FIG. 6B by the same method as (6) of the first embodiment.

  Next, a through hole 203 having a diameter of 100 μm reaching the wiring conductor 201 of the substrate body 200 is formed by a THG-YAG laser so as to be concentric with the through conductor 11 having a diameter of 200 μm (FIG. 6C). Then, a catalyst is applied to the inside of the through hole 203 to perform electroless plating, and further, electrolytic plating is performed to fill the through hole 203 with Cu to form a connection conductor 202. As shown in FIG. The capacitor built-in substrate of the example was completed.

  A terminal is brought into contact with the connection conductor 202 electrically connected to the first capacitor electrode 21 of the capacitor and the connection conductor 202 connected to the second capacitor electrode 22, and a voltage of 1V is applied to insulate the capacitor. When the resistance was measured, it was confirmed that the resistance value exceeded 1 GΩ in all 10 samples, and a sufficient insulation resistance value was obtained.

  The said Example 1, 2 is only an example for implementing this invention, and it cannot be overemphasized that this invention is not limited to this. Changes can be made as appropriate within the scope of the present invention, and for example, the following points can be changed.

(A) Material The material of the dielectric layer is not limited to BaTiO ₃ , and SrTiO ₃ , Pb (Zr, Ti) O _3, etc. may be used. The material of the conductor layer is not limited to Ni, and Cu, Ag, or the like may be used. The substrate body is not limited to the epoxy substrate, and may be a ceramic multilayer substrate or the like.

(B) Firing method In the above examples, firing was performed using a firing-assisting green sheet, but it was used only for the convenience of firing and is not an essential constituent element of the present invention. It is also preferable that the capacitor be fired by using a setter made of Al ₂ O ₃ or the like, as described in the example of Japanese Patent Application No. 2005-122597, for example, without using the firing-assisting green sheet.

(C) Method of forming through conductor In the above embodiment, the through conductor was formed by filling a part of the conductor green sheet by pressure bonding and firing inside the through hole formed in the dielectric green sheet. The inside may be filled with a conductive paste by a method such as printing. By doing so, the conductor is more reliably filled in the through hole, which is particularly effective when the dielectric layer is relatively thick.

(D) Method of forming a through hole In the examples, a THG-YAG laser or a CO ₂ laser is used, but the present invention is not limited to laser processing, and drilling or etching may be used. Even when the through hole is formed by a method other than the laser, if the through hole is directly formed in the dielectric layer, the characteristics of the dielectric layer are adversely affected, so the effectiveness of the present invention remains unchanged.

It is the top view and sectional drawing which show the capacitor | condenser which concerns on this invention. It is sectional drawing which shows the board | substrate with a built-in capacitor | condenser concerning this invention. It is sectional drawing which shows the manufacturing process of the capacitor | condenser which concerns on this invention, and a board | substrate with a built-in capacitor | condenser. It is sectional drawing which shows the manufacturing process of the board | substrate with a built-in capacitor | condenser which concerns on this invention. It is sectional drawing which shows the manufacturing process of the capacitor | condenser of a comparative example. It is sectional drawing which shows the manufacturing process of the board | substrate with a built-in capacitor | condenser of 2nd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dielectric layer 11 Through-conductor 12 Through-hole 21 1st capacity electrode 22 2nd capacity electrode 31 1st electrode pad 32 2nd electrode pad 100 Capacitor 200 Substrate body 201 Wiring conductor 202 Connection conductor 210 Resin hardened material

Claims (8)

A dielectric layer; a first capacitor electrode formed on one main surface of the dielectric layer; and a second capacitor electrode formed on the other main surface of the dielectric layer;
The dielectric layer has a through conductor extending from one main surface to the other main surface, and a through hole is formed inside the through conductor.   The capacitor according to claim 1, wherein the dielectric layer, the first and second capacitor electrodes, and the through conductor are sintered simultaneously. A substrate body having a wiring conductor;
A capacitor according to claim 1 or claim 2;
The board | substrate with a built-in capacitor | condenser characterized by the said through-conductor and the said wiring conductor being electrically connected by the connection conductor formed in the inside of the said through-hole.   The capacitor built-in substrate according to claim 3, wherein the connection conductor is formed by wet plating. Preparing a dielectric green sheet comprising a dielectric powder and a binder and having a through hole, and a conductor green sheet comprising a metal powder and a binder;
Forming a laminate by stacking and crimping the conductor green sheet on both main surfaces of the dielectric green sheet so as to cover at least part of the through hole; and
Firing the laminate and obtaining a fired body having a through conductor in which a part of the conductor green sheet is filled in the through hole; and
And a step of forming a through hole penetrating the through conductor. Preparing a substrate body having a wiring conductor;
Placing the capacitor according to claim 1 or 2 on the substrate body;
Forming a connection conductor inside the through hole, and electrically connecting the through conductor and the wiring conductor by the connection conductor. Preparing a dielectric green sheet comprising a dielectric powder and a binder and having a through hole, and a conductor green sheet comprising a metal powder and a binder;
Forming a laminate by stacking and crimping the conductor green sheet on both main surfaces of the dielectric green sheet so as to cover at least part of the through hole; and
Firing the laminate and obtaining a fired body having a through conductor in which a part of the conductor green sheet is filled in the through hole; and
Placing the fired body on a substrate body having a wiring conductor;
Forming a through hole penetrating at least the through conductor;
Forming a connection conductor inside the through hole, and electrically connecting the through conductor and the wiring conductor by the connection conductor.   8. The method of manufacturing a capacitor built-in substrate according to claim 6, wherein the connection conductor is formed by wet plating.