JP2005045094A - Multilayer capacitor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniature laminate capacitor and its manufacturing method wherein a cut surface of a laminate film capacitor element is protected. <P>SOLUTION: An insulator layer 7 of a metal oxide is formed on the tip end of a metal layer 3 in the vicinity of the cut surface 6 of the laminate capacitor obtained by laminating the metal layer 3 and a dielectric layer 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multilayer capacitor including a dielectric layer and a metal thin film layer, and more particularly to a multilayer capacitor that can be suitably used for an element using an organic film or an organic thin film as a dielectric layer, and a method for manufacturing the same.

  In recent years, along with miniaturization of electronic equipment and high-density mounting, electronic components have been miniaturized and chips have been promoted, and even in film capacitors, which are one of electronic components, multilayer capacitors in which dielectric thin films are laminated. Has been developed, and a capacitor using an organic film as a dielectric (hereinafter referred to as “laminated film capacitor”) has been widely used.

The multilayer film capacitor is obtained by cutting a long capacitor base material in which external electrodes are formed on both end faces of a capacitor portion that is a metal layer and a dielectric layer. If the cut surface resulting from the cutting of the capacitor base material is left exposed, moisture may enter from the cut surface, resulting in a capacitance change or damage to the capacitor due to moisture absorbed during reflow processing after mounting. is there. For this reason, conventionally, the entire laminated film capacitor element is externally covered with a resin, or the cut surface is protected by directly applying the resin to the cut surface (see Patent Documents 1 and 2).
Japanese Patent Publication No. 5-63096 Japanese Patent Laid-Open No. 3-64012

  However, the conventional technique has the following problems. That is, when the exterior is made of resin, the exterior dimension of the multilayer film capacitor is increased because the exterior is formed not only on the cut surface of the multilayer film capacitor element but also on the entire multilayer film capacitor element. It was.

  Further, as shown in FIG. 4, when the resin 140 is directly applied to the cut surface 120 of the multilayer film capacitor element 110 using the roller 150, the roller 150 may physically damage the cut surface 120. The insulation structure of the capacitor portion 112 of the multilayer film capacitor element 110 may be damaged. Further, when the resin 140 is applied by the roller 150, the thickness of the resin 140 becomes about several tens of μm to 100 μm, which makes it difficult to reduce the thickness. Therefore, it is difficult to further reduce the size. It was.

Further, in this method, since application is performed using a roller, when applying to a more miniaturized multilayer film capacitor element 110 (for example, a multilayer film capacitor element having an area of the cut surface 120 of 10 mm ² or less), the element In many cases, it is technically difficult to uniformly apply the resin 140 to each cut surface. Further, since the thickness of the resin 140 with respect to the dimensions of the element becomes relatively large, problems such as mounting defects on the substrate and peeling off of the resin 140 also occur.

  The present invention is intended to solve such problems, and its main purpose is to provide a multilayer capacitor having a small size and high reliability and a method for manufacturing the same, ensuring insulation of the cut surface of the multilayer capacitor element. There is to do.

  The present invention provides a capacitor portion formed by laminating a metal layer and a dielectric layer, and a long electrode formed at both ends of the capacitor portion in the laminating direction and electrically connected to the metal layer of the capacitor portion. In the multilayer capacitor element formed by cutting a long capacitor base material perpendicularly to the longitudinal direction, a non-conductive layer is formed at the tip of the metal layer near the cut surface. This prevents the change of the capacitor capacity by preventing the metal layer from deteriorating due to moisture permeation or moisture absorption during the reflow process after mounting.

  The multilayer capacitor of the present invention is characterized in that the constituent element of the non-conductive layer contains the constituent element of the metal layer. To prevent an electrical short circuit between the metal layers.

  The multilayer capacitor of the present invention is characterized in that the non-conductive layer is made of an oxide or nitride of the metal layer, and the metal layer is used as a modifying substance, thereby The tip in the vicinity of the cut surface is subjected to a non-conductive process.

  The multilayer capacitor of the present invention is characterized in that the constituent element of the non-conductive layer includes the constituent element of the dielectric, and the element constituting the dielectric layer and the element constituting the metal layer By this reaction, the tip in the vicinity of the cut surface of the metal layer is processed to be nonconductive.

  The method for manufacturing a multilayer capacitor according to the present invention is such that the dielectric layer of the multilayer capacitor element is made of an organic film or an organic thin film, and the multilayer capacitor element is cut by irradiating the cut surface of the multilayer capacitor element with plasma. A non-conductive layer is formed at the tip of the metal layer in the vicinity of the surface, and the plasma generates oxidizing or nitriding excited atoms or excited molecules from the organic film or organic thin film on the cut surface. The tip of the metal layer near the cut surface is modified to a non-conductive layer by chemically reacting the excitation plasma with the metal layer constituent atoms. According to the present invention, a non-conductive layer can be formed at the tip of the metal layer without causing physical damage from the outside to the cut surface, thereby ensuring insulation of the cut surface and preventing moisture from entering from the cut surface. It is possible to prevent deterioration of the metal layer.

  According to the multilayer capacitor manufacturing method of the present invention, no physical external force is applied to the cut surface even when the thickness of the dielectric layer is 1 μm or less or the thickness of the metal layer is 50 nm or less. Since a non-conductive layer can be formed at the tip of the metal layer in the vicinity of the cut surface, an electrical short circuit between the metal layers of the thin film laminate that easily damages the capacitor performance can be effectively prevented.

  As described above, according to the present invention, it is possible to prevent the infiltration of moisture from the cut surface and the deterioration of the metal layer due to moisture absorption during the reflow process after mounting, thereby suppressing the change in the capacitor capacity, and insulating the cut surface. Thus, it is possible to provide a small multilayer capacitor that can ensure the performance and a method for manufacturing the same.

  Hereinafter, a multilayer capacitor and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings.

  First, the multilayer capacitor according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view schematically showing the whole multilayer capacitor, and FIG. 2 is a schematic diagram showing a cross section near the cut surface of the multilayer capacitor.

  In FIG. 1, a laminated film capacitor element 1 includes a capacitor unit 4 having a structure in which dielectric layers 2 and metal layers 3 made of an organic thin film such as an organic film or an organic material vacuum-deposited film are alternately laminated, External electrodes (metallicons) 5 formed on both side surfaces of the capacitor portion 4 are provided. Reference numeral 16 shown in FIG. 1 denotes a protective layer. The cut surface 6 of the multilayer film capacitor element 1 is positioned on the front surface and the back surface with respect to the two surfaces orthogonal to the external electrodes 5 and parallel to the stacking direction of the capacitor portion 4, that is, the upper surface of the capacitor portion 4. The cut surface 6 is generated when the laminated capacitor capacitor element 1 is obtained by cutting a long capacitor base material. A non-conductive layer 7 (FIG. 2) is formed and disposed at the tip of the metal layer 3 on the cut surface 6 of the multilayer film capacitor element 1 shown in FIG. The non-conductive layer 7 serves to prevent the metal layer 3 from deteriorating due to moisture permeation from the cut surface 6 or moisture absorption during reflow processing after mounting.

  In the present embodiment, from the viewpoint of increasing the capacity of the capacitor, the organic thin film (film) functioning as the dielectric layer 2 of the capacitor unit 4 is formed from a vacuum vapor deposited film of an ultraviolet curable resin that can be cured by radical polymerization reaction. ing. Instead of the ultraviolet curable resin, an electron beam curable resin or a thermosetting resin can be used. Further, aluminum is used as the metal layer 3 sandwiching the dielectric layer 2, and the external electrode 5 is made of brass or zinc. The dielectric layer 2 is not limited to an ultraviolet curable resin, an electron beam curable resin, or a thermosetting resin made of a vacuum-deposited thin film, and may be formed of a polyester film, a PET film, a PPS film, or the like. Moreover, as a material which comprises the metal layer 3, it is not limited to aluminum, For example, you may use Ni.

The dimension of the multilayer film capacitor element 1 is not particularly limited, but the interval between the external electrodes 5 is about 0.5 to 5 mm, and the interval between the cut surfaces 6 is about 1.0 to 5.0 mm. The area of 6 is about 1.0 to 10 mm ² . In the present embodiment, the laminated film capacitor element 1 having an interval between the external electrodes 5 of 1.6 mm, an interval between the cut surfaces 6 of 3.2 mm, and an area of the cut surface of 5.12 mm ² was used.

  Next, a method for forming the nonconductor layer 7 will be described. FIG. 3 is a schematic cross-sectional view of a plasma processing apparatus used in the multilayer capacitor manufacturing method according to the embodiment of the present invention.

  In FIG. 3, plasma 8 using oxygen gas as a raw material is irradiated onto the cut surface 6 of the multilayer film capacitor element 1, reacts with the metal layer 3, and reaches a depth of about 50 μm at the tip of the metal layer 3. A non-conductive layer 7 is generated. The dielectric layer 2 is an organic thin film made of an ultraviolet curable resin, and the plasma 8 is mainly composed of an oxidizing oxygen plasma. The organic thin film also generates oxidizing excited atoms or excited molecules. The excited plasma containing oxygen as a main component and the constituent atoms of the metal layer 3 are chemically reacted to modify the tip of the metal layer 3 near the cut surface 6 to the non-conductive layer 7. The plasma processing apparatus shown in FIG. 3 includes a vacuum chamber 9, a plasma cathode 11 disposed inside the vacuum chamber 9, means for making the cut surface 6 of the metal layer 3 face the plasma cathode 11, and a vacuum chamber 9. The plasma generating gas inlet 13 connected to the vacuum chamber 9, the exhaust port 14 for evacuating the interior 10 of the vacuum chamber 9, and the plasma generating high-frequency power source 15 connected to the plasma cathode 11. In the method according to the present embodiment, the oxygen plasma irradiation is performed in a vacuum. However, for example, arc-shaped oxygen plasma may be irradiated under an atmospheric pressure. Alternatively, a non-conductive layer 7 made of a metal nitride may be generated at the tip of the metal layer 3 by irradiating with plasma using nitrogen gas as a raw material.

  Below, the specific example in this embodiment is demonstrated.

  In the multilayer capacitor composed of “protective layer 16 / capacitor portion (element layer) 4 / protective layer 16” as shown in FIG. 1, non-conductive layer 7 is formed on metal layer 3 in the vicinity of cut surface 6 as shown in FIG. Formed.

The inside of the vacuum vessel (not shown) was 2 × 10 ⁻⁴ Torr, and a cylindrical rotating body (not shown) for forming a laminate was provided therein.

  First, a portion to be the protective layer 16 was laminated on the cylindrical surface of the cylindrical rotating body. An ultraviolet curable resin was used as a protective layer material, which was vaporized and deposited on a rotating cylindrical surface. The above protective layer material was polymerized and cured using an ultraviolet curing device each time one layer was deposited. This operation was repeated by rotating the cylindrical surface to form a protective layer 16 having a thickness of 15 μm on the cylindrical surface.

  Next, an element layer (capacitor portion) 4 composed of a dielectric layer 2 and a metal (thin film) layer 3 was laminated. The same dielectric layer material as that of the protective layer 16 was used, and this was vaporized and deposited on the protective layer 16. The dielectric layer material deposited as described above was polymerized and cured using an ultraviolet curing device each time one layer was deposited. The dielectric layer per layer formed at this time is 0.4 μm. Further, each time the rotating body is rotated, the metal layer 3 is formed by depositing aluminum from a metal evaporation source while forming an electrically insulating portion by a mask patterning method. The metal deposition thickness is 300 Å.

  The above operation was repeated about 2000 times by rotating the cylinder to form a laminated body portion having a total thickness of 860 μm. The mask patterning was performed in the following pattern every time the rotation in the direction perpendicular to the rotational movement direction of the cylindrical surface was performed once. That is, when the rotating cylinder makes one rotation, it moves 1000 μm in a certain direction, moves 940 μm in the reverse direction after the next one rotation, moves 1000 μm in the reverse direction after the next one rotation, and 940 μm in the reverse direction after the next one rotation. Moves, moves 1000 μm in the reverse direction after the next rotation, moves 1060 μm in the reverse direction after the next rotation, moves 1000 μm in the reverse direction after the next rotation, and moves 1060 μm in the reverse direction after the next rotation This movement was repeated in the following. Thus, the element layer 4 as shown in FIG. 1 was obtained.

  Finally, a protective layer 16 having a thickness of 15 μm was formed on the surface of the element layer 4. The formation method was exactly the same as the formation method of the protective layer. The degree of cure of the dielectric layer 2 of the element layer 4 and the protective layer 16 was 90% or more, respectively.

  Next, the obtained cylindrical laminated body was divided in the radial direction (cut every 45 °), removed, and pressed under heating to obtain a flat laminated mother element. This was cut in parallel to the patterning direction to obtain a strip-shaped mother element. The external electrode 5 was formed by metal spraying brass on the cut surface. Furthermore, a conductive paste in which copper powder was dispersed in a thermosetting phenolic resin was applied to the metal sprayed surface, heat-cured, and further, molten solder plating was applied to the resin surface. Then, it cut | disconnected in the location corresponding to the cut surface 6 of FIG. 1, and obtained the chip-shaped multilayer capacitor.

  Next, the cut surface 6 of the obtained chip-shaped multilayer capacitor is irradiated with oxygen plasma to form aluminum oxide at a depth of 50 μm at the tip of the metal layer 3 to form the non-conductive layer 7 shown in FIG. Then, a modified layer was obtained as a protective portion for preventing the penetration of moisture or the like from the outside at the tip of the aluminum thin film as the metal layer 3 on the cut surface 6 perpendicular to the cross section of the external electrode formation.

  In the multilayer capacitor according to the present embodiment, a plasma processing method as shown in FIG. 3 was used in order to form the nonconductive layer 7 at the tip of the metal layer 3 in the vicinity of the cut surface 6 as shown in FIG.

  In FIG. 3, the vacuum chamber interior 10 was evacuated to 1 Torr or less from an exhaust port 14 connected to a vacuum exhaust pump (not shown). Next, the multilayer capacitor chip was held so that the cut surface 6 was opposed to the flat plasma cathode 11 supported in the vacuum chamber interior 10. Next, the inside of the vacuum chamber was held at 10 Torr by a pressure regulator (not shown) connected to the exhaust port 14 while oxygen gas was introduced from the gas inlet 13 via a flow rate controller (not shown). In this state, 5 to 10 kw of electric power was supplied from the high frequency power source 15 to the plasma cathode 11 to generate oxygen gas plasma 8 in a space formed by the plasma cathode and the cut surface. Irradiation of oxygen gas plasma 8 causes an oxidative organic gas plasma to be locally generated inside the cut surface while reacting with the organic thin film, and reacts with the metal layer 3 of the multilayer film capacitor 1 to cause the tip of the aluminum metal layer. A non-conductive layer 7 mainly composed of aluminum oxide, which is a metal oxide, was formed at a depth of about 50 μm. In addition, this non-conductive substance includes an organic substance dissolved mixed crystal. A chip capacitor having undergone the above processing is subjected to an initial electrical performance inspection, and then a plurality of pieces are placed in a bag and vibrated to apply external force to the cut surface 6 and then reflow after mounting. Although the treatment was performed, in the subsequent electrical performance inspection, no alteration of the metal layer due to moisture absorption was observed, and the capacitor capacity was stable, unchanged from the initial state.

1 is a perspective view schematically showing a multilayer capacitor in an embodiment of the present invention. It is sectional drawing which shows typically the cut surface of the multilayer capacitor in one Embodiment of this invention. It is explanatory drawing which shows typically the manufacturing method of the multilayer capacitor in one Embodiment of this invention. It is the schematic which shows the cut surface protection method of the conventional multilayer capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multilayer capacitor element 2 Dielectric layer 3 Metal layer 4 Capacitor part 5 External electrode 6 Cut surface 7 Non-conductive layer

Claims (8)

A long capacitor comprising a capacitor part formed by laminating a metal layer and a dielectric layer, and an external electrode formed in the lamination direction at both ends of the capacitor part and electrically connected to the metal layer of the capacitor part A multilayer capacitor comprising a base material cut perpendicularly to a longitudinal direction, wherein a non-conductive layer is formed at a tip of a metal layer near the cut surface. The multilayer capacitor according to claim 1, wherein a constituent element of the metal layer is included in a constituent component of the nonconductive layer. 3. The multilayer capacitor according to claim 2, wherein the non-conductive layer is made of an oxide or nitride of the metal layer. 4. The multilayer capacitor according to claim 2, wherein a constituent element of the dielectric is included in a constituent component of the nonconductive layer. The dielectric layer of the multilayer capacitor element is composed of an organic film or an organic thin film. By irradiating the cut surface of the multilayer capacitor element with plasma, a non-conductive layer is formed at the end of the metal layer near the cut surface of the multilayer capacitor element. A method for manufacturing a multilayer capacitor, comprising: forming a multilayer capacitor. 6. The method for manufacturing a multilayer capacitor according to claim 5, wherein the non-conductive layer is an oxide or nitride of the metal layer. 7. The multilayer capacitor according to claim 5, wherein a thickness of the dielectric layer is 1 μm or less. The multilayer capacitor according to claim 5, 6 or 7, wherein the metal layer has a thickness of 50 nm or less.

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