In order to enhance versatility, a chip-type battery having a means for readily identifying a first terminal and a second terminal is provided. The chip-type battery includes: a body having a substantially rectangular parallelepiped shape and contains a plurality of power generating elements in a stack, each element including a sintered material; a first terminal having a first polarity; and a second terminal having a second polarity. The first terminal is provided at a first side face of the body. The second terminal is provided at a second side face of the body located on other than the first side face. The first terminal and the second terminal include different metal materials.

BACKGROUND OF THE INVENTION

The present invention relates to a chip-type battery comprising a plurality of power generating elements which are stacked, each element containing a sintered material.

As electronic devices become more and more compact, more electronic components are constructed in the form of chips and they are densely mounted on printed circuit boards. Usually, the electronic components are mounted by reflow soldering. With the increased demand for lead-free electronic devices in recent years, lead-free soldering has become popular for use. Lead-free soldering requires a reflow temperature of about 240° C., which is higher than the conventional reflow temperature of about 200° C. Under the circumstances, electrolytic capacitors containing an electrolyte have gradually been replaced with chip-type all solid state electrolytic capacitors. In addition to this, there are proposed chip-type batteries that can be directly mounted on substrates (Japanese Laid-Open Patent Publication No. Hei 6-231796).

Electrochemical devices such as electrolytic capacitors and batteries have a polarity. Accordingly, when they are used, it is necessary to identify a cathode, or positive electrode, and an anode, or negative electrode. For example, if the polarity of a terminal cannot be identified when an electrochemical device having a polarity is mounted on a substrate, the electrochemical device might be mounted with the anode and the cathode reversed.

FIG. 1is a perspective view of a typical chip-type electrochemical device. This chip-type electrochemical device has a symmetric structure, and comprises a body11having a substantially rectangular parallelepiped shape, a first terminal12and a second terminal13, each terminal arranged at the end of the body11. This type of shape is adopted into multilayer ceramic capacitors, functional polymer electrolytic aluminum capacitors, etc, which have been commercialized.

Multilayer ceramic capacitors do not have a polarity, and therefore there is no need to identify a first terminal and a second terminal. Functional polymer electrolytic aluminum capacitors and tantalum capacitors, however, do have a polarity, and therefore a first terminal and a second terminal must be identified.

In view of this, in order to identify a first terminal and a second terminal, there is proposed to print, with the use of an ink, a mark24for indicating the polarity of a first terminal22or a second terminal23on a body21of an electrochemical device as shown inFIG. 2. Such a mark, however, is not applicable to electrochemical devices produced through sintering process. This is because, since the mark should be printed in the early stages of the production process and the sintering process is usually performed in the latter stages of the production process, the mark printed using an ink is evaporated during the sintering process.

Meanwhile, some electrochemical devices not having a stacked structure have an asymmetric structure with a first terminal and a second terminal of different shapes. A tantalum solid electrolytic capacitor (F95 series manufactured by Nichicon Corporation) shown inFIG. 3, for example, has a cathode terminal32and an anode terminal33of different shapes arranged at the ends of a body31. The body31comprises a device part35and an outer coating resin36for covering the device part35. From the cathode-terminal-side end of the device part35is protruded a cathode lead34. Likewise, a tantalum solid electrolytic capacitor (T491 series manufactured by KEMET Corporation) shown inFIG. 4is characterized by the shape of the end of a body41. The body41comprises a device part45and an outer coating resin46for covering the device part45. The end of the outer coating resin46where a cathode terminal42is disposed has a different shape from the end of the same where an anode terminal43is disposed. It is, however, difficult to adopt the structures described above into electrochemical devices comprising a plurality of power generating elements which are stacked.

Another approach is proposed to address the step of mounting an electrochemical device on a substrate. For example, a solid electrolytic capacitor shown inFIG. 5is proposed in which a cathode terminal52is formed in the center of a body51and anode terminals53are respectively formed at the ends of the body51(Japanese Laid-Open Patent Publication No. Hei 6-232011). Although the purpose is different, there is also proposed a capacitor as shown inFIG. 6in which a dent67is formed at an end of a body61having a cathode terminal62so that a cathode lead64is exposed from the dent67. Because the cathode terminal62has a different shape from an anode terminal63in this capacitor, it is easy to identify the polarity (Japanese Laid-Open Patent Publication No. Hei 7-115041). However, in this case also, it is difficult to adopt such a structure into electrochemical devices comprising a plurality of power generating elements which are stacked.

Meanwhile, Japanese Laid-Open Patent Publication No. Hei 11-26297 proposes to house a chip-type capacitor in an outer case71having a substantially rectangular parallelepiped shape as shown inFIG. 7. The outer case71is provided with an L-shaped first terminal electrode74extending from a first side face72to a bottom face73and an L-shaped second terminal electrode76extending from a second side face75, which is positioned opposite to the first side face72, to the bottom face73. The first terminal electrode74and the second terminal electrode76are formed such that they are in positions displaced from the symmetric position in the outer case71. The capacitor housed in the outer case71is a surface-mounted capacitor using no connecting lead wire. Accordingly, even if an attempt is made to mount it on a circuit board such that the first terminal electrode and the second terminal electrode are reversed, because the position of each terminal on the circuit board does not correspond to that of each electrode on the case, reverse connection can be prevented.

Moreover, Japanese Laid-Open Patent Publication No. Hei 11-26297 proposes to house an electrochemical device in an outer case81having a substantially rectangular parallelepiped shape as shown inFIG. 8. The outer case81is provided with an L-shaped first terminal electrode84extending from a first side face82to a bottom face83and a second terminal electrode86extending from a second side face85, which is positioned opposite to the first side face82, to the bottom face83. In this case, even if the capacitor housed in the outer case81is mounted on a circuit board with its polarity reversed, the first terminal electrode84and the second terminal electrode86do not come in contact with the terminals on the circuit board.

The use of the outer cases as shown inFIGS. 7 and 8, however, requires an increased number of components as well as an increased cost of equipment because it necessitates two different processes: the process to provide the cathode terminal and the process to provide the anode terminal. In other words, the use of the outer cases as shown in the figures is accompanied by the problem of increasing the production cost.

As can be clearly understood from the above, a versatile means for readily identifying a first terminal and a second terminal for a chip-type battery comprising a plurality of power generating elements which are stacked, each element containing a sintered material, has not yet been proposed.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a chip-type battery comprising: a body having a substantially rectangular parallelepiped shape and containing a plurality of power generating elements which are stacked, each element comprising a sintered material; a first terminal having a first polarity; and a second terminal having a second polarity, wherein the first terminal is provided at a first side face of the body, the second terminal is provided at a second side face of the body which is located on other than the first side face, and the first terminal and the second terminal comprise different metal materials.

In this embodiment, the first terminal and the second terminal preferably comprise different metals capable of absorbing lights at different wavelengths.

The present invention further relates to a chip-type battery comprising: a body having a substantially rectangular parallelepiped shape and containing a plurality of power generating elements which are stacked, each element comprising a sintered material; a first terminal having a first polarity; a second terminal having a second polarity; and a marking member for identifying the polarity of the first terminal and the second terminal, wherein the first terminal is provided at a first side face of the body, the second terminal is provided at a second side face of the body which is located on other than the first side face, the marking member is attached to the outer surface of at least one selected from the group consisting of the first terminal, the second terminal and the body, and the marking member possesses the identification function even at a sintering temperature to obtain the sintered material.

In this embodiment, it is preferred to use a magnetic material as the marking member, more preferably a paint containing a magnetic material.

The present invention is particularly advantageous for chip-type batteries where a combination comprising a body having a substantially rectangular parallelepiped shape, and a first terminal and a second terminal has a shape which is symmetric with respect to at least one plane.

According to the present invention, it is possible to provide a versatile means for readily identifying a first terminal and a second terminal for a chip-type battery comprising a plurality of power generating elements which are stacked, each element comprising a sintered material at low cost. Moreover, according to the present invention, it is possible to efficiently prevent reverse connection when the chip-type batteries described above are mounted on integrated circuit boards (IC boards), large-scale integrated circuit boards (LSI boards), etc.

Preferred embodiments of the present invention will be described below referring to the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1 will be described referring toFIG. 9. This embodiment relates to a chip-type battery comprising a body91having a substantially rectangular parallelepiped shape and containing a plurality of power generating elements which are stacked, a first terminal92having a first polarity and a second terminal93having a second polarity. Each power generating element comprises a sintered material. The first terminal92is provided at a first side face of the body91. The second terminal93is provided at a second side face positioned opposite to the first side face. The battery as a whole is symmetric in shape with respect to the center of the body91.

In this embodiment, the first terminal and the second terminal comprise different metal materials. Because different metal materials have different physical properties (e.g. absorbance wavelength, density, specific resistance, magnetism and the like) depending on the type of metal materials, the first terminal and the second terminal can be identified using the physical properties as the indication. The first terminal and the second terminal may be identified by an identification device. Depending on the physical property used for the indication, the identification may be done visually. The metal materials used for the first terminal and the second terminal preferably have good solder wettability.

For example, when the first terminal is made of tin, nickel, zinc or silver, the second terminal is preferably made of copper, brass or phosphor bronze.

The mounting of chip-type batteries on printed circuit boards are usually automated. For this reason, the mounting device should automatically identify the first terminal and the second terminal. For example, the addition of the function to detect a physical property such as absorbance wavelength, density, specific resistance or magnetism of the first or second terminal so as to identify the first terminal or the second terminal to the mounting device can prevent reverse connection of the batteries during the mounting process. Particularly when the first terminal and the second terminal are made of different metal materials having different absorbance wavelength in the visible light region, the terminals can be identified visually. In mass production, automatic identification can be done by an image sensor.

The whole terminal need not necessarily be made of one metal, and it may comprise a plurality of metals. For example, it is effective to plate the surface of the first terminal and that of the second terminal with different metals. It is also effective to plate either one of the first terminal and the second terminal with a metal different from the substrate metal.

FIG. 10is a vertical sectional view of a chip-type battery having plated-terminals. This chip-type battery comprises a body131having a substantially rectangular parallelepiped shape and comprising a stack of a plurality of power generating elements136and an outer material135for covering or housing the stacked power generating elements136. Each of the stacked power generating elements136comprises a first electrode136aand a second electrode136bwith a solid electrolyte136cinterposed between the first electrode136aand the second electrode136b.

A first terminal132having a first polarity is formed at a first side face of the body131. A second terminal133is formed at a second side face of the same. The first terminal and the second terminal are plated with different metals. More specifically, the first terminal comprises a substrate metal132aand a first plating layer132bformed on the surface of the substrate metal132a. The second terminal comprises a substrate metal133aand a second plating layer133bformed on the surface of the substrate metal133a. In the case of the substrate metal132aof first terminal being made of, for example, nickel, the substrate metal132ais preferably plated with, for example, tin to form the first plating layer132b. Likewise, In the case of the substrate metal133aof second terminal being made of, for example, nickel, the substrate metal133ais preferably plated with, for example, copper to form the second plating layer133b.

A chip-type battery according to Embodiment 2 will be described with reference toFIG. 11. The chip-type battery shown inFIG. 11comprises a body101having a substantially rectangular parallelepiped shape, a first terminal102having a first polarity and a second terminal103having a second polarity.

The first terminal102is provided at a first side face of the body101. The second terminal103is provided at a second side face positioned opposite to the first side face. The body101, the first terminal102and the second terminal103are combined such that the first terminal102and the second terminal103are symmetric with respect to the center of the body101. In this embodiment, a button-shaped member104serving as an marking member is attached to the outer surface of the second terminal103.

Although the marking member is button-shaped inFIG. 11, it may be in any shape as long as the marking member can be detected visually or by a machine. For example, as shown inFIG. 12, a rectangular parallelepiped-shaped member114may be attached. The rectangular parallelepiped-shaped member114may be attached to the outer surface of either a first terminal112or a second terminal113, each provided at the end of a body111. The marking member may be made of the same material as the terminal, or of a different material. In either case, the material for the marking member should have the identification function even at a sintering temperature to obtain the sintered material constituting the power generating elements. Examples of such material include: rare-earth magnets (i.e. magnets containing a rare-earth element) such as Sm—Co based rare-earth magnet and Nd—Fe—B based rare-earth magnet; magnetic materials composed of oxides such as Ba-ferrite and Sr-ferrite; mixtures of a coloring component and a glass frit; and glazes for porcelain. As the coloring component, a compound containing Mn, Fe, Co, Ni, Ru, etc or a pigment can be used. Ferrite-based magnetic materials are particularly suitable for the marking member because they are characterized by low cost and excellent sinterability. The mixtures of a coloring component and a glass frit and the glazes excel in improving visual identification because these materials can impart shine to the marking member.

The method for attaching the marking member to the outer surface of a terminal is not specifically limited. The marking member can be adhered to the terminal with an adhesive, or welded thereto using a laser, or it can be attached by magnetic force.

In this embodiment, the first terminal and the second terminal may be made of different metal materials, or of the same metal material. For example, the first terminal and the second terminal may be made of nickel, and the marking member may also be made of nickel.

Besides the surface of a terminal as shown inFIGS. 11 and 12, the marking member can be attached to the outer surface of the body in the proximity of one terminal. Specifically, as shown inFIG. 13, a rectangular parallelepiped-shaped member124or a marking member having other shape can be attached to the outer surface of a body121in the proximity of a first terminal122or a second terminal123, each terminal provided at the end of the body121. Because the terminals are formed in the latter stages of the battery production process, the effect of the present invention is enhanced when the marking member is attached to the body. Optionally, a plurality of marking members may be attached to the outer surface of a terminal or that of the body in the proximity of the terminal.

The marking member may be a film made of a paste containing a conductive powder. For example, a paste mixture comprising a conductive powder and a resin is applied to the terminal or the body, and the conductive power may be sintered to the terminal or the body during the sintering process of power generating elements.

A chip-type battery according to Embodiment 3 will be described with reference toFIG. 14. The chip-type battery shown inFIG. 14comprises a body141having a substantially rectangular parallelepiped shape, a first terminal142having a first polarity and a second terminal143having a second polarity. This battery has the same structure as the battery of Embodiment 2 except that it has a marking member of different type.

In this embodiment, a magnetic material144serving as a marking member is attached to the body141in the proximity of a second terminal143. More specifically, a paste containing a powdered magnetic material is applied to a certain portion of the body, followed by drying or sintering to attach the magnetic material to the body. The paste can be prepared by, for example, mixing a powdered magnetic material, a binder and a solvent. An example of the binder for use includes polyvinyl butyral. An example of the solvent includes butyl acetate.

When a magnetic material is used as the marking member, the polarity of terminal can be identified visually, or by the presence or intensity of magnetism. Examples of suitable magnetic material that can be applied to the terminal or the like include Ba-ferrite and Sr-ferrite.

As described above, the present invention is a chip-type battery suitable to be mounted on an IC board or LSI board containing a plurality of power generating elements which are stacked, each element comprising a sintered material, and the battery has a means for readily identifying terminals.