JP2005072465A - Ceramic vessel and tantalum electrolytic capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic vessel for a tantalum electrolytic capacitor and the tantalum electrolytic capacitor using this where the airtightness of a capacitor element can be held when the tantalum electrolytic capacitor is exposed to high temperature in the case of soldering and where miniaturization is possible. <P>SOLUTION: The ceramic vessel 6 is provided with a ceramic base substance 3. At the center of the upper surface of the base substance 3, a rectangular parallelepiped recessed part 3-B is formed. On the bottom surface of the base substance 3, a first metallizing layer 3a and a second metallizing layer 3b are formed independently from each other. On the lower surface of the base substance 3, a first conductor layer 3c and a second conductor layer 3d are formed independently from each other. The ceramic vessel 6 is also provided with a first connection conductor 3e for electrically connecting the first metallizing layer 3a with the first conductor layer 3c, and a second connection conductor 3f for electrically connecting the second metallizing layer 3b with the second conductor layer 3d. The first metallizing layer 3a consists of a wide width part 31 and a narrow width part 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tantalum electrolytic capacitor used for an electronic circuit or the like, and more particularly to a tantalum electrolytic capacitor configured using a ceramic container.

  A surface mount type tantalum electrolytic capacitor is known as a conventional resin-encapsulated solid electrolyte capacitor. This tantalum electrolytic capacitor is used in large quantities in a wide range of fields including communication equipment such as mobile phones, AV equipment such as digital cameras, computer equipment such as personal computers, and automobile equipment such as airbags and antilock brakes. Applications include power supply smoothing circuits, computer backups, timer circuits using charging / discharging time of tantalum electrolytic capacitors, high frequency filters, and the like, which are indispensable electronic components for the above equipments.

  Such a tantalum electrolytic capacitor includes a tantalum electrolytic capacitor element portion, a lead frame, and an exterior resin that hermetically seals the lead frame, and the lead frame generally has a strength such as an iron (Fe) -nickel (Ni) alloy. Is used, and as the exterior resin, an epoxy resin or the like is used because of its good heat resistance and moisture resistance.

  A conventional tantalum electrolytic capacitor of this type will be described below with reference to FIG. FIG. 3 is a cross-sectional view showing the structure of a conventional tantalum electrolytic capacitor, in which 11 is a tantalum electrolytic capacitor, 12 is a tantalum electrolytic capacitor element, 12b is an anode lead, and the tantalum electrolytic capacitor element 12 is made of tantalum or the like. One end portion of the anode lead 12b is embedded, and a sintered body 12a obtained by sintering a compact made of tantalum powder embedded so that the other end portion protrudes from the side surface is sintered on a dielectric oxide film layer ( (Not shown), a solid electrolyte layer (not shown) is formed outside the oxide film layer, and then a cathode layer 12c is formed on the outer periphery.

  The other end of the anode lead 12b is welded to the lead frame 13, and the lead frame 13 protrudes from the exterior resin 14 and is bent along the outer shape of the exterior resin 14 to reach the lower surface. Is done. Further, the lead frame 13 is bonded onto the cathode layer 12c via the conductive bonding material 15, and protrudes from the outer resin 14 and is bent along the outer shape of the outer resin 14 to reach the lower surface of the outer resin 14. The cathode terminal 13b for connection is used. In order to bend the lead frame 13 to be a connection terminal for both poles, and to be able to be bent at the same time, the lead frame 13 has a structure that is protruded in both directions from the same height of the opposite side surfaces of the exterior resin 14. Yes. As the exterior resin 14, an epoxy resin is used because of its excellent heat resistance, moisture resistance, and the like.

  Next, a method for manufacturing the tantalum electrolytic capacitor 11 will be described. First, the tantalum electrolytic capacitor element 12 is mounted on the fixed portion 16 of the tantalum electrolytic capacitor element 12 in the lead frame 13, and the anode lead 12b and the anode terminal 13a of the tantalum electrolytic capacitor element 12 are joined to each other by welding. The cathode layer 12b of the capacitor element 12 and the cathode terminal 13b are bonded via a thermosetting conductive bonding material 15. For example, a silver (Ag) epoxy resin bonding material is used as the conductive bonding material 15 and is cured by heating at a temperature of about 300 ° C. for about 10 minutes.

Further, the tantalum electrolytic capacitor element 12 to which the lead frame 13 is bonded is placed at a predetermined position, and then the tantalum electrolytic capacitor element 12 is exposed so that the end portion that becomes the bonded portion with the external electric circuit board is exposed to the outside. A part of the lead frame 13 is coated with an exterior resin 14 made of epoxy, and the exterior resin 14 is cured by heating at 150 to 180 ° C. for about 1 hour. As a result, the polymer crosslinking ratio of the exterior resin 14 is increased, the heat resistance and moisture resistance are improved, and the highly reliable tantalum electrolytic capacitor 11 is obtained. Next, the lead frame 13 is bent downward along the outer shape of the exterior resin 14 so that the anode terminal 13a and the cathode terminal 13b are located on the lower surface of the tantalum electrolytic capacitor 11, thereby constituting a part of the lower surface of the tantalum electrolytic capacitor 11. To do. This facilitates mounting on an external electric circuit board and can be suitable for mass production.
JP 2002-134360 A (page 3-4, FIG. 1)

  In recent years, solders that do not use lead (Pb) have been used as the awareness of global environmental problems has increased. However, the solder containing no Pb has a soldering temperature of 40-50 compared to the conventional solder processing temperature (220-230 ° C.) of Pb (lead) 40% -Sn (tin) 60%. When the soldering is performed at this temperature, the exterior resin 14 is altered by heat and a gap is formed between the lead frame 13 and moisture enters the gap to generate a leakage current or short circuit. It has a problem of causing defects.

Therefore, it has been studied to add a filler such as silica (SiO ₂ ) or alumina (Al ₂ O ₃ ) to the exterior resin 14 to impart high heat resistance. In this case, the thermal expansion coefficient of the exterior resin 14 is considered. And the difference from the thermal expansion coefficient of the lead frame 13 is increased, so that a gap is generated between the lead frame 13 and the exterior resin 14 at the temperature when soldering, and moisture enters and the above-mentioned defect occurs. This method is not practical.

Furthermore, the use of a highly heat-resistant resin such as polyimide as the exterior resin 14 has also been studied. In addition to the expensive material, polyimide has a coefficient of thermal expansion that is the coefficient of thermal expansion of the lead frame 13 (7 × 10 ⁻ 60 × 10 ⁻⁶ / ° C., which is more than eight times that of ⁶ / ° C.), so that there is still a problem that a gap is generated between the lead frame 13 and the exterior resin 14, leading to the above-mentioned defect. It was.

  Further, since the conventional tantalum electrolytic capacitor 11 has a structure in which the lead frame 13 protrudes from the exterior resin 14, it has become impossible to meet the recent demand for downsizing of the tantalum electrolytic capacitor 11.

  Therefore, the present invention has been completed in view of the above problems, and its purpose is to maintain the airtightness of the tantalum electrolytic capacitor element even when the tantalum electrolytic capacitor is exposed to a high temperature. An object is to provide a tantalum electrolytic capacitor that can be reduced in size.

  In the ceramic container of the present invention, a rectangular parallelepiped recess is formed at the center of the upper surface, the first metallized layer and the second metallized layer are formed independently of each other on the bottom surface of the recess, and the first is formed on the lower surface. A ceramic base on which the conductor layer and the second conductor layer are formed independently of each other; the first connection conductor for electrically connecting the first metallized layer and the first conductor layer; And a second connecting conductor for electrically connecting the second conductor layer, the first metallized layer comprising a wide portion and a narrow portion. .

  The tantalum electrolytic capacitor of the present invention includes a ceramic container having the above structure, an anode lead terminal having one end embedded in a side surface of a sintered body of tantalum powder and the other end welded to the narrow portion, and A tantalum electrolytic capacitor element having a cathode layer deposited on the lower surface of the sintered body and electrically connected to the second metallized layer, and attached to the upper surface of the ceramic base so as to close the recess. And a covered lid.

  According to the ceramic container of the present invention, the rectangular parallelepiped recess is formed at the center of the upper surface, the first metallization layer and the second metallization layer are formed independently from each other on the bottom surface of the recess, and the first A ceramic substrate in which one conductor layer and a second conductor layer are formed independently of each other, and a first connection conductor and a second metallization that electrically connect the first metallization layer and the first conductor layer. A solder that does not contain Pb, since the first metallized layer includes a wide portion and a narrow portion. Even if the first conductor layer and the second conductor layer are electrically connected to the external electric circuit board using the ceramic substrate, the ceramic base body is heat resistant and thus hardly deforms by heat, and a gap is generated in the ceramic container. To maintain good airtightness Kill. Therefore, it is possible to effectively prevent moisture from entering the inside of the ceramic container, and to effectively prevent leakage current and occurrence of short circuit failure.

  Therefore, compared with the airtightness of the conventional structure with exterior resin and lead frame, the airtight reliability is much higher. When the tantalum electrolytic capacitor element is housed inside, the tantalum electrolytic capacitor element malfunctions due to corrosion due to moisture, etc. Can be effectively prevented, and the electrical characteristics of the tantalum electrolytic capacitor element can be well maintained over a long period of time.

  Further, by accommodating the tantalum electrolytic capacitor element inside the ceramic container, it is possible to configure the tantalum electrolytic capacitor without using a lead frame, so that it is possible to significantly reduce the size as compared with the conventional tantalum electrolytic capacitor. .

  Furthermore, since the first metallized layer is composed of a wide part and a narrow part, when the anode lead terminal of the tantalum electrolytic capacitor element is welded to the first metallized layer by a welding method, the temperature tends to be high in the narrow part, Only the portion that contacts the narrow portion of the anode lead terminal can be preferentially melted. Therefore, the anode lead terminal can be easily welded and joined to the first metallized layer, and the anode lead terminal can be selectively joined only to the narrow portion 30 of the first metallized layer to reduce the joining area. It can be effectively suppressed. As a result, the anode lead terminal can be efficiently and reliably electrically connected to the external electric circuit, and the resistance value fluctuation due to the variation in the bonding area between the anode lead terminal and the first metallized layer can be effectively prevented, and the accuracy can be improved. It can have a good resistance value.

  A tantalum electrolytic capacitor according to the present invention includes a ceramic container having the above structure, an anode lead terminal in which one end is embedded in a side surface of a sintered body of tantalum powder and the other end is welded to a narrow portion, and sintered. A tantalum electrolytic capacitor element having a cathode layer deposited on the lower surface of the body and electrically connected to the second metallization layer; and a lid mounted on the upper surface of the ceramic base so as to close the recess. By providing, the airtight reliability using the ceramic container of the present invention is high. In addition, since it can be manufactured by a multi-cavity method using a known ceramic green sheet lamination method, it is extremely excellent in mass productivity. Furthermore, since no lead frame is used, the size can be greatly reduced as compared with a conventional tantalum electrolytic capacitor.

  The ceramic container and tantalum electrolytic capacitor of the present invention will be described in detail below. FIG. 1A is a top view showing an example of an embodiment of the ceramic container of the present invention, and FIG. 1B is a cross-sectional view of the ceramic container of FIG. FIG. 2 is a cross-sectional view showing an example of an embodiment of the tantalum electrolytic capacitor of the present invention. In these drawings, 1 is a tantalum electrolytic capacitor, 2 is a tantalum electrolytic capacitor element, 3 is a ceramic substrate, 3a is a first metallized layer, 30 is a narrow part, 31 is a wide part, 3b is a second metallized layer, 3c is a first conductor layer, 3d is a second conductor layer, 3e is a first connection conductor, 3f is a second connection conductor, 4 is a lid, and 6 is a ceramic container.

  In the ceramic container 6 of the present invention, a rectangular parallelepiped recess 3-B is formed at the center of the upper surface, and the first metallization layer 3a and the second metallization layer 3b are formed independently of each other on the bottom surface of the recess 3-B. The first and second conductor layers 3c and 3d are independently formed on the lower surface of the ceramic base 3, and the first metallized layer 3a and the first conductor layer 3c. One connection conductor 3e and a second connection conductor 3f formed from the second metallized layer 3b to the second conductor layer 3d. The first metallized layer 3a includes a wide portion 31 and a narrow portion. It consists of 30 and.

  The ceramic container 6 has the anode lead terminal 2b of the tantalum electrolytic capacitor element 2 welded to the narrow portion 30 of the first metallized layer 3a and the cathode of the tantalum electrolytic capacitor element 2 to the second metallized layer 3b. The layer 2c is electrically joined, and the lid 4 is attached to the upper surface of the side wall 3-A of the ceramic substrate 3 so as to close the recess 3-B, whereby the tantalum electrolytic capacitor 1 is obtained.

  The ceramic substrate 3 is made of ceramics such as an alumina sintered body, and has a recess 3-B formed at the center of the upper surface. Preferably, as shown in FIG.1 (b), the site | part in which the 1st metallization layer 3a is formed should become the convex part 3-C. The convex portion 3-C is formed and the first metallized layer 3a is formed on the upper surface thereof, whereby the electrical connection of the anode lead 2b of the tantalum electrolytic capacitor element 2 to the first metallized layer 3a is easy. Thus, the working efficiency of connecting the anode lead 2b of the tantalum electrolytic capacitor element 2 to the first metallized layer 3a is greatly improved.

The ceramic container 6 is produced as follows, for example. When the ceramic substrate 3 is made of an alumina sintered body, an organic binder suitable for a raw material powder such as aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), magnesium oxide (MgO), calcium oxide (CaO), A solvent is added and mixed to form a slurry. This slurry is formed into a green sheet by a doctor blade method or a calender roll method and cut into a required size. Next, an appropriate punching process is performed in order to form the convex portion 3-C in a plurality of green sheets selected from them.

  Then, a metal paste mainly composed of a metal powder such as tungsten (W) is printed and applied to these green sheets, and the first and second metallized layers 3a and 3b, and the first and second conductor layers 3c and 3d. Next, a green sheet on which these conductor layers are formed is laminated, and a metal paste for forming the first and second connection conductors 3e and 3f is applied to the outer surface. The ceramic container 6 is produced by firing at a temperature.

  The first and second connection conductors 3e and 3f may be through conductors formed in the ceramic base 3.

  Moreover, the exposed surface of these conductor layers formed in the ceramic container 6 thus produced is a metal excellent in corrosion resistance and excellent in wettability with solder, specifically having a thickness of 1 to 12 μm. A nickel (Ni) layer and a gold (Au) layer having a thickness of 0.3 to 5 μm are preferably sequentially deposited by a plating method or the like. Thereby, in the first and second conductor layers 3c and 3d, the wettability with the solder is improved, and the bonding strength with the electrode (not shown) on the external electric circuit board becomes stronger.

  If the thickness of the Ni layer is less than 1 μm, it becomes difficult to prevent the oxidative corrosion of each conductor made of the metallized layer, and the bonding strength to the external electric circuit board tends to deteriorate. On the other hand, if the thickness of the Ni layer exceeds 12 μm, it takes a long time to form the plating, so that the mass productivity is likely to be lowered and the electric resistance is likely to be increased.

  In addition, if the thickness of the Au layer is less than 0.3 μm, it is difficult to form an Au layer having a uniform thickness, and a portion where the Au layer is extremely thin or a portion where the Au layer is not formed is generated. Therefore, the effect of preventing oxidative corrosion and the wettability with solder are likely to decrease. On the other hand, if the thickness of the Au layer exceeds 5 μm, it takes a long time to form the plating, and the mass productivity tends to decrease.

  The ceramic container 6 accommodates the tantalum electrolytic capacitor element 2 inside, and the first and second conductor layers 3c and 3d on the lower surface are Au-Sn solder or the like on the wiring conductor on the surface of the external electric circuit board (not shown). By joining via solder such as Ag—Sn solder, the tantalum electrolytic capacitor element 2 housed inside and the wiring conductor of the external electric circuit board can be electrically connected.

  The first metallized layer 3 a of the present invention includes a wide portion 31 and a narrow portion 30. With this configuration, when the anode lead terminal 2b of the tantalum electrolytic capacitor element 2 is welded to the narrow portion 30 of the first metallized layer 3a, the temperature tends to be high at the narrow portion 30, and the narrow portion 30 of the anode lead terminal 2b is formed. The contact site can be preferentially dissolved. That is, when the welding is resistance welding, since the resistance value is increased at the narrow portion 30, heat is likely to be generated at the narrow portion 30, and the narrow portion 30 can be satisfactorily joined to the anode lead terminal 2b. it can. Further, when the welding is laser welding, it becomes difficult for the heat of the laser to diffuse in the narrow portion 30, and the narrow portion 30 can be satisfactorily joined to the anode lead terminal 2b. Accordingly, the anode lead terminal 2b can be easily welded and joined to the first metallized layer 3a, and the anode lead terminal 2b is selectively joined only to the narrow portion 30 of the first metallized layer 3a to reduce the joining area. It is possible to effectively suppress variation. As a result, the anode lead terminal 2b can be efficiently and reliably electrically connected to the external electric circuit, and the resistance value variation due to the variation in the bonding area between the anode lead terminal 2b and the first metallized layer 3a can be effectively prevented. And having an accurate resistance value.

  The narrow portion 30 may be formed in any part of the first metallized layer 3a. When the convex portion 3-C is formed on the bottom surface of the concave portion 3-B and the first metallized layer 3a is provided on the top surface of the convex portion 3-C, the second metallized layer 3b side is located. The end of one metallized layer 3a is preferably a narrow portion 30. Thereby, one end is embedded in the side surface of the sintered body 2a of tantalum powder, and the anode lead terminal 2b can be connected to the narrow portion 30 at the shortest distance, and the connection position is shifted due to deformation of the anode lead terminal 2b. Can be effectively suppressed.

  Preferably, 0.1 A ≦ B ≦ 0.8 A, where B is the width of the narrow portion 30 and A is the width of the wide portion 31. With this configuration, when the anode lead terminal 2b of the tantalum electrolytic capacitor element 2 is welded by resistance welding, it is possible to preferentially dissolve the portion that contacts the narrow portion 30 of the anode lead terminal 2b. The terminal 2b can be further easily welded. If B <0.1A, the width of the narrow portion 30 becomes too narrow and the bonding area with the anode lead terminal 2b becomes very small, and the anode lead terminal 2b is firmly attached to the first metallized layer 3a. It becomes difficult to join to. When B> 0.8A, the width of the narrow portion 30 becomes too wide, and when the anode lead terminal 2b is welded by resistance welding, the portion that contacts the narrow portion 30 of the anode lead terminal 2b is preferential. It becomes difficult to dissolve in.

  The narrow portion 30 is preferably larger than the width of the anode lead terminal 2b. As a result, when the anode lead terminal 2b and the narrow portion 30 are welded, the anode lead terminal 30 melts and spreads to the narrow portion 30 to form a large meniscus, and the anode lead terminal 2b and the narrow portion are formed. The bonding strength with 30 can be made stronger.

  The tantalum electrolytic capacitor 1 of the present invention includes a ceramic container 6 having the above structure and an anode in which one end is embedded in the side surface of the sintered body 2a of tantalum powder and the other end is welded to the first metallized layer 3a. A tantalum electrolytic capacitor element 2 having a lead terminal 2b and a cathode layer 2c attached to the lower surface of the sintered body 2a and bonded to the second metallized layer 3b via a conductive adhesive 5, and ceramic A lid 4 is provided on the upper surface of the base 3 so as to close the recess 3-B.

  The tantalum electrolytic capacitor element 2 is a sintered body obtained by sintering a molded body in which one end of an anode lead 2b made of tantalum or the like is embedded and the other end protrudes from a side surface and solidified with tantalum powder. A dielectric oxide film layer (not shown) is formed on the bonded body 2a, a solid electrolyte layer (not shown) is formed outside the oxide film layer, and then a cathode layer 2c is formed on the outer periphery.

  The other end of the anode lead 2b is electrically connected to the first metallized layer 3a by a welding method such as resistance welding or laser welding. The first metallized layer 3a is electrically connected to the first conductor layer 3c via the first connection conductor 3e. That is, the first conductor layer 3c becomes an anode terminal for external connection.

  The cathode layer 2c is electrically connected to the second metallized layer 3b through a conductive bonding material 5 such as an Ag epoxy resin bonding material. The second metallized layer 3b is electrically connected to the second conductor layer 3d via the second connection conductor 3f. That is, the second conductor layer 3d becomes a cathode terminal for external connection.

  According to the tantalum electrolytic capacitor 1 of the present invention configured as described above, even if the first and second conductor layers 3c and 3d are electrically connected to the external electric circuit board using solder not containing Pb. Since the ceramic substrate 3 has heat resistance, it is difficult to be deformed by heat, and it is possible to prevent gaps from being generated in the ceramic container 6 and maintain good airtightness. Therefore, it is possible to effectively prevent moisture from entering the inside of the ceramic container 6 and to effectively prevent leakage current and short circuit from occurring.

  Therefore, compared with the airtightness in the configuration having the conventional exterior resin and lead frame, the airtight reliability is much higher, and it is possible to effectively prevent the tantalum electrolytic capacitor element 2 from malfunctioning due to corrosion due to moisture and the like. The electrical characteristics of the electrolytic capacitor element 2 can be favorably maintained over a long period.

  Further, by providing both the first and second conductor layers 3c and 3d electrically connected to the anode lead terminal 2b and the cathode layer 2c of the tantalum electrolytic capacitor 1 on the lower surface of the ceramic substrate 3, a lead frame or the like is provided. It can be easily connected by surface mounting to the wiring conductor on the surface of the external electric circuit board without using it, and there is no need to bend the lead frame. The size can be greatly reduced compared to a capacitor.

  Furthermore, since the ceramic container 6 can be manufactured by a multi-cavity method using a known ceramic green sheet lamination method, the ceramic container 6 is extremely excellent in mass productivity.

  Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, although the case where the material of the ceramic substrate 3 of the tantalum electrolytic capacitor 1 is an alumina sintered body has been described, it may be made of other ceramics such as an aluminum nitride (AlN) sintered body or glass ceramics. In the case of being made of an AlN sintered body, heat during operation can be efficiently dissipated to the outside, so that the electrical characteristics of the tantalum electrolytic capacitor 1 can be maintained for a longer period.

  The tantalum electrolytic capacitor of the present invention can be used in a wide range of fields including communication equipment such as mobile phones, AV equipment such as digital cameras, computer equipment such as personal computers, and automobile equipment such as airbags and antilock brakes.

(A) is a top view which shows an example of embodiment of the ceramic container of this invention, (b) is sectional drawing of the ceramic container of (a). It is sectional drawing which shows an example of embodiment of the tantalum electrolytic capacitor of this invention. It is sectional drawing of the conventional tantalum electrolytic capacitor.

Explanation of symbols

1: Tantalum electrolytic capacitor 2: Tantalum electrolytic capacitor element 2a: Sintered body 2b: Anode lead terminal 2c: Cathode layer 3: Ceramic substrate 3a: First metallized layer 3b: Second metallized layer 3c: First conductor layer 3d: second conductor layer 3e: first connection conductor 3f: second connection conductor 3-B: concave portion 4: lid 5: conductive adhesive 6: ceramic container
30: Narrow part
31: Wide part

Claims (2)

A rectangular parallelepiped recess is formed at the center of the upper surface, the first metallized layer and the second metallized layer are formed independently of each other at the bottom of the recess, and the first conductor layer and the second metallized layer are formed on the lower surface. A ceramic substrate having conductor layers formed independently of each other, a first connection conductor that electrically connects the first metallized layer and the first conductor layer, the second metallized layer, and the second And a second connecting conductor for electrically connecting the first metallized layer to the first conductive layer, wherein the first metallized layer comprises a wide portion and a narrow portion. The ceramic container according to claim 1, an anode lead terminal having one end embedded in a side surface of the sintered body of tantalum powder and the other end welded to the narrow portion, and a lower surface of the sintered body A tantalum electrolytic capacitor element having a cathode layer deposited and electrically connected to the second metallization layer; and a lid attached to the upper surface of the ceramic base so as to close the recess. A tantalum electrolytic capacitor comprising:

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