Patent Publication Number: US-2009237868-A1

Title: Capacitor device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Applicants claim priority under 35 U.S.C. §119 of Japanese Patent Application No. 2008-069520 filed Mar. 18, 2008. 
     BACKGROUND OF THE INVENTION 
     This invention relates to a capacitor device which comprises a capacitor element and connection members for the capacitor element. 
     High operation frequency in recent years requires smoothness of power supply and tolerance to high frequency noise. To meet the requirements, a large number of capacitors each of which has large capacitance and low impedance are used in an electric apparatus. For example, several tens of ceramic capacitors are used as “decoupling capacitors or bypass capacitors” in one apparatus. Normally, the total area required to mount the capacitors thereon becomes large in accordance with the increased number of the capacitors mounted. Therefore, there is a need to a capacitor device which has large capacitance and low impedance but does not require a large implementation area therefor. 
     To meet the above-mentioned low impedance requirement, JP 2002-299161 discloses a hybrid device which comprises a capacitor element and an IC (integrated circuit) mounted on the capacitor element. The hybrid device of JP 2002-299161 has low impedance between the capacitor element and the IC. 
     To meet the above-mentioned large capacitance requirement, JP 2002-289470 discloses a capacitor device which comprises a plurality of capacitor elements stacked. In addition, an IC can be mounted and connected to the capacitor device so that low impedance between the capacitor device and the IC also can be achieved. 
     However, each of the disclosed capacitor devices is very specialized for its use so that the whole structure must be changed if the IC is replaced with another structured IC. In other words, the structures of the disclosed capacitor devices are not widely applicable. Therefore, there is a need to a capacitor device which has a widely applicable structure or structural concept while having large capacitance and low impedance. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention provides a capacitor device which comprises first and second substrates and a capacitor element. The capacitor element comprises an anode portion and a cathode portion. The first substrate has a first inner surface and a first outer surface and is provided with a first inner anode terminal, a first inner cathode terminal, a first outer anode terminal and a first outer cathode terminal. The capacitor element is mounted on the first inner surface of the first substrate. The first inner anode terminal and the first inner cathode terminal are formed on the first inner surface and are electrically connected to the anode portion and the cathode portion, respectively. The first outer anode terminal and the first outer cathode terminal are formed on the first outer surface and are electrically connected to the first inner anode terminal and the first inner cathode terminal, respectively. The second substrate has a second inner surface and a second outer surface and is provided with a second inner anode terminal, a second inner cathode terminal, a second outer anode terminal and a second outer cathode terminal. The second inner surface is mounted on the capacitor element so that the capacitor element is positioned between the first and the second substrates. The second inner anode terminal and the second inner cathode terminal are formed on the second inner surface and are electrically connected to the anode portion and the cathode portion, respectively. The second outer anode terminal and the second outer cathode terminal are formed on the second outer surface and are electrically connected to the second inner anode terminal and the second inner cathode terminal, respectively. 
     An appreciation of the objectives of the present invention and a more complete understanding of its structure may be had by studying the following description of the preferred embodiment and by referring to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view schematically showing a capacitor device according to a first embodiment of the present invention, wherein the capacitor device comprises first and second substrates and a capacitor element. 
         FIG. 2  is a view schematically showing the capacitor element of  FIG. 1 . 
         FIG. 3  is a set of plan views schematically showing the first substrate of  FIG. 1 , wherein the left figure shows a first outer surface of the first substrate while the right figure shows a first inner surface of the first substrate. 
         FIG. 4  is a cross-sectional view schematically showing the first substrate of  FIG. 3 . 
         FIG. 5  is a set of plan views schematically showing the second substrate of  FIG. 1 , wherein the left figure shows a second outer surface of the second substrate while the right figure shows a second inner surface of the second substrate. 
         FIG. 6  is a cross-sectional view schematically showing the second substrate of  FIG. 5 . 
         FIG. 7  is a perspective view schematically showing a capacitor element of a capacitor device according to a second embodiment of the present invention. 
         FIG. 8  is a view schematically showing the capacitor element of  FIG. 7 , wherein the capacitor element is partially cut off along lines A-A. 
         FIG. 9  is a set of plan views schematically showing a first substrate for the capacitor element of  FIG. 7 , wherein the left figure shows a first outer surface of the first substrate while the right figure shows a first inner surface of the first substrate. 
         FIG. 10  is a set of plan views schematically showing a second substrate for the capacitor element of  FIG. 7 , wherein the left figure shows a second outer surface of the second substrate while the right figure shows a second inner surface of the second substrate. 
         FIG. 11  is a cross-sectional view schematically showing a capacitor device according to a third embodiment of the present invention. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     First Embodiment 
     With reference to  FIG. 1 , a capacitor device  1  according to a first embodiment of the present invention comprises a capacitor element  10 , a first substrate  20  and a second substrate  30 . The capacitor element  10  is positioned between the first substrate  20  and the second substrate  30 . For example, each of the first substrate  20  and the second substrate  30  may be mainly made of glass epoxy, liquid crystal polymer or polyimide. 
     With reference to  FIG. 2 , the capacitor element  10  comprises a base member  13 , dielectric layers  14 , dividers  15 , a first cathode conductive layer  60   a , a second cathode conductive layer  60   b , and lead-frames  19 . 
     In detail, the base member  13  is made of a valve metal. In this embodiment, the valve metal is aluminum so that the capacitor element  10  is an aluminum solid electrolytic capacitor element. The base member  13  generally has a plate shape or a film shape. In addition, the base member  13  of the present embodiment has a porous structure, i.e. a large surface area. The dielectric layers  14  of the present embodiment are oxide layers which are obtained by exposing a mother material of the base member  13  to a chemical conversion or chemical oxidization process. In this embodiment, the base member  13  with the dielectric layers  14  is an aluminum film with alumina layers and has a capacitance per unit area of 220 μF/cm 2 , a nominal chemical conversion voltage of 3 V and a thickness of 70 μm. 
     The dividers  15  are formed on the dielectric layers  14  so that each dielectric layer  14  is divided into three regions; two end regions correspond to anode portions  11 , while a middle region between the dividers  15  corresponds to a cathode portion  12 . In this embodiment, the dividers  15  are made of insulator, specifically, resin such as epoxy resin. Note here that the end regions of the dielectric layers  14  are removed in a posterior process, as mentioned afterwards, so that the illustrated capacitor element  10  does not have the end regions of the dielectric layers  14  but has only the middle regions of the dielectric layers  14 . 
     Each of the first cathode conductive layer  60   a  and the second cathode conductive layer  60   b  is formed on the dielectric layer  14 , especially the middle region between the dividers  15  so that the first cathode conductive layer  60   a  and the second cathode conductive layer  60   b  are electrically insulated from the base member  13 . The first cathode conductive layer  60   a  and the second cathode conductive layer  60   b  are electrically connected to each other on at least one end surface of the capacitor element  10 . Each of the first cathode conductive layer  60   a  and the second cathode conductive layer  60   b  constitutes the cathode portion  12 . Each of the first cathode conductive layer  60   a  and the second cathode conductive layer  60   b  of the present embodiment comprises a solid electrolyte layer  16 , a graphite layer  17  and a silver layer  18  which are stacked in this order. In this embodiment, the solid electrolyte layer  16  is made of conductive polymer. 
     The end regions of the dielectric layers  14  are removed so that end regions of the base member  13  are exposed. On the exposed end regions of the base member  13 , the lead-frames  19  are formed through an ultrasonic welding process. Each lead-frame  19  serves as an anode conductive layer which constitutes the anode portion  11 . Each lead-frame  19  of the present embodiment is made of a Ni/Cu/Ag plated cupper film. Thus, the capacitor element  10  is obtained. 
     With reference to  FIGS. 3 and 4 , the first substrate  20  has a first outer surface  21  and a first inner surface  22 . On the first inner surface  22 , the capacitor element  10  is mounted (also see  FIG. 1 ). The first outer surface  21  of the first substrate  20  according to the present embodiment is mounted on a circuit board when the capacitor device  1  is used. Needless to say, an IC may be connected to the first outer surface  21  directly or through a circuit board. 
     The first substrate  20  is provided with a first outer anode terminal, a first outer cathode terminal, first inner anode terminals  25  and a first inner cathode terminal  26 . In this embodiment, the first outer anode terminal consists of first outer anode contacts  23 , while the first outer cathode terminal consists of first outer cathode contacts  24 . The first inner anode terminals  25  and the first inner cathode terminal  26  are formed on the first inner surface  22 . The first inner anode terminals  25  are electrically connected to the anode portions  11 , while the first inner cathode terminal  26  is electrically connected to the cathode portion  12 , specifically, the first cathode conductive layer  60   a  (also see  FIGS. 1 and 2 ). The connections between the first inner anode terminals  25  and the anode portions  11  and the connection between the first inner cathode terminal  26  and the cathode portion  12  are established by means of conductive adhesives  40  in the present embodiment (also see  FIG. 1 ). The first outer anode contacts  23  and the first outer cathode contacts  24  are formed on the first outer surface  21 . Specifically, the first outer anode contacts  23  and the first outer cathode contacts  24  are alternately arranged on the first outer surface  21  in accordance with the present embodiment. The first outer anode contacts  23  and the first outer cathode contacts  24  are electrically connected to the first inner anode terminal  25  and the first inner cathode terminal  26 , respectively, by means of through-holes which are formed in the first substrate  20 , as shown in  FIG. 4 . 
     With reference to  FIGS. 5 and 6 , the second substrate  30  has a second outer surface  31  and a second inner surface  32 . The second inner surface  32  is mounted on the capacitor element  10  (also see  FIG. 1 ). The second outer surface  31  of the present embodiment is configured to mount an additional capacitor device thereon, as explained below. Therefore, the second outer surface  31  allows easy increase of a total capacitance per unit implementation area. 
     The second substrate  30  is provided with a second outer anode terminal  33 , a second outer cathode terminal  34 , second inner anode terminals  35  and a second inner cathode terminal  36 . The second inner anode terminals  35  and the second inner cathode terminal  36  are formed on the second inner surface  32 . The second inner anode terminals  35  are electrically connected to the anode portions  11 , respectively, while the second inner cathode terminal  36  is electrically connected to the cathode portion  12 , specifically, the second cathode conductive layer  60   b  (also see  FIGS. 1 and 2 ). The connections between the second inner anode terminals  35  and the anode portions  11  and the connection between the second inner cathode terminal  36  and the cathode portion  12  are established by means of conductive adhesives  40  in the present embodiment (also see  FIG. 1 ). The second outer anode terminal  33  and the second outer cathode terminal  34  are formed on the second outer surface  31 . The second outer anode terminal  33  and the second outer cathode terminal  34  are electrically connected to the second inner anode terminals  35  and the second inner cathode terminal  36 , respectively, by means of through-holes which are formed in the second substrate  30 , as shown in  FIG. 6 . 
     In this embodiment, the number of the second outer anode terminal  33  is one, and the number of the second outer cathode terminal  34  is also one, as shown in  FIG. 5 . However, the present invention is not limited thereto. The number of the second outer anode terminal  33  may be two or more, and the number of the second outer cathode terminal  34  may be one or more. For example, if an additional capacitor device to be mounted on the capacitor device  1  has outer terminals similar to the capacitor element  10 , the number of the second outer anode terminals  33  is two, while the number of the second outer cathode terminal  34  is one; in other words, they may have the same arrangement as that of the second inner anode terminals  35  and the second inner cathode terminal  36  of the present embodiment. 
     In this embodiment, the capacitor element  10  is fixed to the first substrate  20  and the second substrate  30  through a thermocompression bonding process by using the conductive adhesives  40 . In addition, the capacitor element  10  fixed to the first substrate  20  and the second substrate  30  is covered by applying liquefied epoxy resin  50  to the peripherals of the capacitor element  10 , followed by curing the epoxy resin  50 . Thus, the capacitor device I of the present embodiment can be obtained, as shown in  FIG. 1 . 
     The capacitor device  1  of the present embodiment, especially the first substrate  20  has a multiple outer contact structure consisting of the first outer anode contacts  23  and the first outer cathode contacts  24 , wherein the first outer anode contacts  23  and the first outer cathode contacts  24  are alternately arranged. The alternate arrangement of the first outer anode contacts  23  and the first outer cathode contacts  24  solves or decreases undesirable magnetic fields so that the capacitor device  1  can have a low ESL (Equivalent Series Inductance). 
     According to the present embodiment, the function of the capacitor device and the external connection function of the capacitor device are separated. Even if a circuit board and/or an additional capacitor device has a different arrangement or structure of electrodes, the design change of the first and/or the second substrate  20 ,  30  allows the different arrangement without changing the design of the capacitor element  10 . In other words, the capacitor element  10  can be applicable to various kinds of circuit boards and/or additional capacitor devices only by changing the design of the first and/or the second substrate  20 ,  30 . In addition, the capacitor element  10  can has a simple structure which has no through-holes therein. Therefore, the capacitor device of the present embodiment has a reliable capacitance function with low cost. 
     Second Embodiment 
     With reference to  FIGS. 7 to 10 , a capacitor device according to a second embodiment of the present invention is a modification of the above-mentioned capacitor device of the first embodiment. Therefore, in  FIGS. 7 to 10 , the similar reference numbers are given to the structures same as or similar to those of the capacitor device of the first embodiment. For example, dividers  15   a  correspond to the dividers  15  of the first embodiment. In this connection, the description will be directed only to the differences between the first and the second embodiments. 
     With reference to  FIGS. 7 and 8 , a capacitor element  10   a  of the present embodiment comprises, as an anode portion, a plurality of anode sections  11   a . The anode sections  11   a  are formed on four end portions of the base member  13 . The anode sections  11   a  of the present embodiment are arranged around a cathode portion  12   a , i.e. first and second cathode conductive layers  60   a ′,  60   b ′, as seen along a direction perpendicular to the base member  13 . The first and second cathode conductive layers  60   a ′,  60   b ′ are electrically connected to each other, the mutual connection is established on and around the corners of the square-shaped cathode portion  12   a.    
     With reference to  FIG. 9 , a first substrate  20   a  has an arrangement of a first inner anode terminal  25   a  and a first inner cathode terminal  26   a  specified for the capacitor element  10   a , although a plurality of first outer anode contacts  23   a  and a plurality of first outer cathode contacts  24   a  are alternately arranged on a first outer surface  21   a  in the same manner as the first embodiment. In detail, the first inner cathode terminal  26   a  has a square shape, while the first inner anode terminal  25   a  has a rectangular frame shape surrounding the first inner cathode terminal  26   a  on a first inner surface  22   a , as seen along the perpendicular direction. 
     With reference to  FIG. 10 , a second substrate  30   a  has an arrangement of a second inner anode terminal  35   a  and a second inner cathode terminal  36   a  specified for the capacitor element  10   a , although a second outer anode terminal  33   a  and a second outer cathode terminal  34   a  have the same arrangement as the first embodiment on a second outer surface  31   a . In detail, the second inner cathode terminal  36   a  has a square shape, while the second inner anode terminal  35   a  has a rectangular frame shape surrounding the second inner cathode terminal  36   a  on a second inner surface  32   a , as seen along the perpendicular direction. 
     The capacitor element  10   a  and the first substrate  20   a  of the present embodiment can decrease an ESL value in comparison with the first embodiment. 
     Third Embodiment 
     With reference to  FIG. 11 , a capacitor device  1   b  according to a third embodiment of the present invention is a modification of the above-mentioned capacitor device of the first embodiment. Therefore, in  FIG. 11 , the similar reference numbers are given to the structures same as or similar to those of the capacitor device of the first embodiment. For example, second outer anode terminal  33   b  and second outer cathode terminal  34   b  correspond to the second outer anode terminal  33  and the second outer cathode terminal  34  In this connection, the description will be directed only to the differences between the first and the third embodiments. 
     Instead of the liquefied epoxy resin  50 , a frame-shaped pre-impregnation sheet  50   b  is used in the present embodiment. Specifically, a pre-impregnation sheet is stamped out so that the frame-shaped pre-impregnation sheet  50   b  is obtained. The frame-shaped pre-impregnation sheet  50   b  has an opening which corresponds to the outer shape of a capacitor element  10   b  of the present embodiment. In the frame-shaped pre-impregnation sheet  50   b , the capacitor element  10   b  is placed. Then, first and second substrates  20   b ,  30   b  are placed on top and bottom surfaces of the capacitor element  10   b  with conductive adhesives  40   b  applied on the predetermined positions such as contacts or terminals. It is preferable that the conductive adhesives  40   b  are semi-cured in this stage. Then, a thermocompression bonding process is carried out so that the capacitor device  1   b  is obtained. For example, the bonding press is carried out under a reduced pressure of 10 Torr and some press conditions of temperature: 170° C.; time: 30 min; and applied pressure: 0.5 MPa. The third embodiment can omit a covering process by using resin because the capacitor element  10   b  can be covered by the frame-shaped pre-impregnation sheet  50   b  simultaneously with the fixation process of the first and the second substrates  20   b ,  30   b  to the capacitor element  10   b.    
     The present application is based on a Japanese patent application of JP2008-069520 filed before the Japan Patent Office on Mar. 18, 2008, the contents of which are incorporated herein by reference. 
     While there has been described what is believed to be the preferred embodiment of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such embodiments that fall within the true scope of the invention.