JP2009004671A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which is a small lower face electrode-type and has a filet face subjected to plating capable of obtaining superior productivity and reliability. <P>SOLUTION: A capacitor element 1 has a cathode layer containing a solid electrolyte layer formed on a dielectric oxide film, in which the dielectric oxide film is formed on a surface of a porous valve action metallic body to be an anode. In a substrate, a crosstie-like anode connection 5 and a cathode connection 6 for the capacitor element are formed on the upper side of a plate-like insulative resin 4, an anode 7 for capacitor mounting face conducting to the crosstie-like anode connection 5 through a via 9 is formed on the lower side of the plate-like insulative resin 4, and a cathode 8 for capacitor mounting face conducting to the cathode connection 6 for the capacitor element through a via 9 is formed on the lower side. The capacitor element 1 is disposed on the substrate, is a solid electrolyte capacitor in which a periphery of it is packaged by a packaging resin 11, and a part of the substrate that is not applied with the resin coating is folded along the side of the packaging resin 11 to form filet faces 12, 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a bottom electrode type solid electrolytic capacitor having an electrode directly drawn on a substrate mounting surface.

  Conventionally, solid electrolytic capacitors using tantalum, niobium or the like as a valve metal are small, have a large capacitance, are excellent in frequency characteristics, and are widely used in CPU decoupling circuits or power supply circuits. In addition, with the development of portable electronic devices, the commercialization of bottom electrode type solid electrolytic capacitors has been progressing.

  When mounting such a bottom electrode type solid electrolytic capacitor on a substrate, a terminal part called a fillet surface on the side surface of the bottom electrode type solid electrolytic capacitor is important together with a terminal part of the substrate mounting surface of the bottom electrode type solid electrolytic capacitor. Become. The reason is that the soldering state including the board mounting surface is inspected by observing the melting state of the solder on the fillet surface after soldering. The problem with this fillet surface is that when the melted solder gets wet, if the product does not get wet evenly on the anode side and the cathode side, the product will be mounted tilted or if the wett on the fillet surface is not enough, This means that the solder collects only on the bottom surface, which is the substrate mounting surface, and the product is lifted up. To prevent this, the fillet surface is usually plated.

  This is a chip-type solid electrolytic capacitor with a structure called a bottom electrode type that uses the lower surface of the lead frame as the capacitor electrode and the cut surface of the lead frame as the fillet surface for the purpose of reducing the product size and thickness. Briefly described. Details thereof are disclosed in Patent Document 1 and the like.

  FIG. 8 shows an internal perspective view before cutting into product dimensions. Further, FIG. 9 shows a view after cutting into product dimensions, FIG. 9 (a) is a side view on the anode side, FIG. 9 (b) is a side view on the cathode side, and FIG. 9 (c) is FIG. It is sectional drawing along the BB line of a) and FIG.9 (b).

  As shown in FIG. 8, the anode lead wire 2 drawn out from the capacitor element 1 is joined to the anode lead frame 82, and the cathode layer of the capacitor element 1 is connected to the cathode lead frame 83 via the conductive adhesive 10. At the same time, it is fixed to the lead frame 82 of the anode via an insulating adhesive 84.

  The fillet surfaces 12 and 13 with good solder wettability are formed by cutting along the alternate long and short dash lines 81a and 81b in the figure and plating the cut surfaces of the lead frames 82 and 83. However, in this manufacturing process, since plating is performed after forming the exterior resin, the manufacturing process becomes complicated, the amount of capital investment increases, the production cost increases, and the characteristics of the capacitor are affected.

  Further, as a method for reducing the size and thickness, there is a technique disclosed in Patent Document 2. This technique has a structure using a substrate (sheet piece) instead of using a lead frame as an electrode terminal. However, since the fillet surface needs to be subjected to a plating process (terminal electrode film formation) after cutting the package body as described above, there is a similar problem. Alternatively, when the terminal electrode film is not formed, there is a problem that a fillet surface having sufficient visibility cannot be obtained.

  There exists patent document 3 as a technique which solves these. FIG. 10 shows an internal perspective view before cutting into product dimensions. The lead frames 104 and 105 are processed into a concave shape, and the inside of the concave portion is plated. When cut by the alternate long and short dash lines 101a and 101b in the figure, the capacitor element side surfaces of the concave portions are exposed to become anode and cathode fillet surfaces 102 and 103, respectively. FIG. 11 shows a view after cutting into product dimensions, FIG. 11 (a) is a side view on the anode side, FIG. 11 (b) is a side view on the cathode side, and FIG. 11 (c) is FIG. 11 (a). FIG. 12 is a cross-sectional view taken along the line CC of FIG. In this method, it is necessary to form the concave portion inside the outer shape of the bottom electrode type solid electrolytic capacitor, and it is difficult to improve the volume efficiency of the capacitor element. In addition, it is difficult to stably form a fillet because it is cut at the recessed portion where plating is formed, and the fillet surface may be scraped if the accuracy of cutting the recessed portion by dicing is not sufficient.

JP 2004-228424 A JP 2001-52961 A JP 2005-197457 A

  The bottom electrode type solid electrolytic capacitor for the purpose of miniaturization and thinning needs to be plated with the fillet surface part after the resin exterior as in Patent Document 1. Product characteristic deterioration, productivity reduction, and capital investment due to fillet surface formation There is a problem of an increase in cost. The technique of Patent Document 2 has the same problem.

  Further, in Patent Document 3 in which a recess is formed in the electrode terminal, a plating treatment surface is provided therein, and the fillet surface is exposed on the side surface of the bottom electrode type solid electrolytic capacitor by cutting it, the bending accuracy of the lead frame, There is a high possibility that the fillet surface will be scraped due to factors such as insufficient cutting accuracy of the concave portion by dicing, and stable production becomes difficult as miniaturization progresses.

  In this situation, an object of the present invention is to provide a solid electrolytic capacitor that is a small bottom electrode type and has a plated fillet surface that is excellent in productivity and reliability.

  The invention of the present application provides means for solving the above-mentioned problems. The structure of the present invention is that a dielectric oxide film is formed on the surface of a porous valve metal body serving as an anode, and the dielectric oxide film is formed on the dielectric oxide film. A capacitor element in which a cathode layer including a solid electrolyte layer is formed has a first conductive layer opposite to the capacitor element formed on one of two main surfaces of a plate-like insulating resin layer, and a mounting terminal on the other A solid electrolysis in which a second conductive layer is formed and disposed on a substrate in which the first and second conductive layers are electrically connected, and an outer peripheral portion of the capacitor element is covered with a resin together with a part of the substrate The capacitor is characterized in that a portion of the substrate not covered with resin is bent along the side surface of the outer resin.

  It is desirable that the thickness of the first conductive layer is thicker than that of the second conductive layer in order to make the fillet forming portion thinner while ensuring an appropriate thickness for the substrate.

  It is desirable that only the second conductive layer is formed on a portion of the substrate that is bent along the side surface of the exterior resin.

  In the present invention, a part of the substrate for forming the bottom electrode type solid electrolytic capacitor is bent into the side surface of the capacitor to form a fillet surface, thereby deteriorating product characteristics and productivity seen in the conventional method of forming the fillet surface by plating. There are no problems such as lowering of the cost, large capital investment, and cost increase. Furthermore, the lead frame is processed into a concave shape, and the inside is plated and cut to expose the fillet surface. .

  Further, by using a substrate in which the first conductive layer is thicker than the second conductive layer, the substrate has sufficient strength that is difficult to break during the manufacturing process, and the thickness of the fillet forming portion is reduced. Can do.

  In addition, by using only the second conductive layer as a portion of the substrate serving as the fillet surface, the dimensional accuracy when the fillet is bent can be increased, and further miniaturization is possible.

  Next, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows the structure of a bottom electrode type solid electrolytic capacitor manufactured according to the present invention. FIG. 1A is a side view of the anode side end face, but the cathode side end face has the same shape. FIG.1 (b) is sectional drawing along the AA line of Fig.1 (a).

  The anode lead wire 2 of the capacitor element 1 and the conductive sleeper 3 are joined by laser welding or resistance welding, and the sleeper 3 and the sleeper anode connection portion 5 of the substrate are joined by the conductive adhesive 10 or laser welding or resistance welding. Join. The cathode portion of the capacitor element 1 is bonded to the capacitor element cathode connection portion 6 of the substrate using the conductive adhesive 10. The exterior resin 11 is formed using a liquid epoxy resin, injection molding, transfer molding, or the like, such as epoxy resin, PPS (polyphenylene sulfide), PEEK (polyether ether ketone), LCP (liquid crystal polymer), etc. It is formed using a heat-resistant resin that can withstand reflow. After the exterior packaging, the substrate portions to be the fillet surfaces 12 and 13 are left by dicing, unnecessary portions are cut together with the exterior resin, and finally the fillet surfaces 12 and 13 portions of the substrate are bent.

  The substrate portion will be described. The substrate is formed with a pattern having conductive portions of sleeper anode connection portion 5 and capacitor element cathode connection portion 6 on the both sides of the insulating resin 4 on the capacitor element connection surface, that is, a first conductive layer, The capacitor mounting electrode surface is formed with a pattern having a conductive portion of the capacitor mounting surface anode 7, the capacitor mounting surface cathode 8, the anode fillet surface 12, and the cathode fillet surface 13, that is, a second conductive layer. Conductive portions of the cathode and anode of the capacitor element connection surface and the capacitor mounting electrode surface are electrically connected by vias 9.

  FIG. 2 is a plan view showing the pattern of the conductive portion on the capacitor element connection surface. The resin sheathing is performed so as not to form the exterior resin on the substrate that becomes the fillet surface outside the two-dot chain line portion 22, and after cutting the substrate and the exterior resin at the one-dot chain line portion 21, the two-dot chain line portion 22 The board portion to be bent is folded toward the front side of the paper. The broken line portion 23 corresponds to the via 9 portion in FIG. The larger the number of vias, the smaller the electrical resistance. However, about 1 to 5 is appropriate considering the cost and the like.

  FIG. 3 is a bottom view showing the pattern of the conductive portion on the capacitor mounting electrode surface. After the substrate and the exterior resin are cut at the alternate long and short dash line portion 21, the substrate portions that become the fillet surfaces 12 and 13 are bent at the two-dot chain line portion 22 in the depth direction of the paper surface. At this time, glass epoxy or polyimide is used as the insulating resin, but LCP, PEEK, or the like can also be used. The thickness is suitably 80 to 10 μm. The conductive portion is obtained by gold plating on copper on both the capacitor element connection surface and the capacitor mounting electrode surface. Therefore, the fillet surfaces 12 and 13 are the same. The thickness is suitably 60 to 10 μm including the plated part.

  In this way, the solid electrolytic capacitor of the present embodiment is obtained. However, in an actual manufacturing process, after a large number of capacitor elements are connected on one substrate, a process of cutting and bending is performed through a resin sheathing process. Do. Details thereof will be described in the following examples.

(Example 1)
Since the capacitor element is manufactured by a known technique, the case where tantalum is used as the valve metal will be described in a simplified manner. Around the tantalum wire, tantalum powder is molded with a press and sintered at high vacuum and high temperature. Next, an oxide film of Ta ₂ O ₅ is formed on the surface of the tantalum metal powder. Further, after being immersed in manganese nitrate, it is thermally decomposed to form MnO ₂ , and subsequently a cathode layer made of graphite and Ag is formed to obtain a capacitor element. If a conductive polymer such as polythiophene or polypyrrole is used instead of MnO ₂ in the cathode layer, it is easy to obtain a low ESR as a capacitor element alone. In addition to tantalum, niobium, aluminum, titanium, or the like can be used as the valve metal.

  The substrate used in this example is about 60 μm of glass epoxy for insulating resin, about 20 μm of gold-plated copper on the conductive part, total thickness of about 100 μm, 20 capacitors × 10 rows = 200 capacitors, The patterns of the element connection surface and the capacitor mounting electrode surface are the same as those shown in FIGS.

  The manufacturing procedure will be described in order. First, referring to FIG. 1, anode lead 2 connected to capacitor element 1 was bonded to sleeper 3 by resistance welding. In this embodiment, the sleeper 3 is a 42 alloy silver-plated product. It is also possible to use copper, stainless steel or the like as the base material of the sleeper 3 and gold, tin, palladium or the like as the plating.

  The epoxy-based conductive adhesive 10 containing silver is applied to the sleeper anode connection part 5 and the capacitor element cathode connection part 6 of the substrate using a dispenser, and the capacitor element welded with the sleeper 3 is mounted thereon, and 150 ° C. Then, it was cured by heating for 30 minutes and adhered to the substrate.

  FIG. 4 illustrates the subsequent production procedure by illustrating the product produced in each step from the front side and the right end side. (1) In the connection step, the state in which the capacitor element and the substrate are connected is shown. The substrate 51 used this time can arrange 10 capacitor elements in the front direction and 20 in the side direction.

  (2) In the resin sheathing process, the state after the resin sheathing is shown. As shown in the front side of the exterior resin, it is necessary to prevent the resin from being formed on the portion of the substrate that becomes the fillet surfaces 12 and 13, so a portion without the exterior resin is provided between the capacitor element rows. There is an uneven shape. On the other hand, the exterior resin is continuously formed on the side surface. In this embodiment, a liquid epoxy resin is used as the exterior resin, the substrate is attached to the mold, the liquid epoxy resin is injected into the mold in a vacuum state, heated at 150 ° C. for 3 minutes, and then the substrate is taken out from the mold. The liquid epoxy resin was cured by heating at 150 ° C. for 3 hours.

  (3) In the cutting step, the state after cutting the substrate and the exterior resin by dicing is shown. In the front view, the substrate is cut leaving the fillet surface portion, and in the side view, the exterior resin and the substrate are cut to the desired product dimensions.

  (4) In the bending step, the state after bending the substrate using a mold is shown. It is completion in this state.

  Instead of bending the fillet surface part of the substrate after it has been cut into product sizes, it is necessary to bend all the fillet surface parts on the substrate with a mold. A method of cutting into sizes is also conceivable. In this method, it is necessary to process the substrate in advance so that the fillet surface portion can be bent.

(Example 2)
Referring to FIG. 5 which is a cross-sectional view of the solid electrolytic capacitor of Example 2, the substrate used in this example is approximately 40 μm in thickness of the insulating resin 4 and the conductive portion (first conductive material) on the capacitor element connection surface. Layer) has a thickness of about 40 μm, and the conductive part (second conductive layer) on the capacitor mounting electrode surface has a thickness of about 20 μm. The thickness of the conductive part is different, and the thickness of the fillet surfaces 12 and 13 is implemented. Compared to Example 1, the total thickness can be reduced by 40 μm per capacitor. Although it is possible to reduce both the thicknesses of the conductive portions, if the substrate is too thin, the probability of breakage during production increases, so an appropriate thickness is required. Other parts are the same as those in the first embodiment.

(Example 3)
The capacitor element connection surface of the substrate used in this example is shown in a plan view in FIG. The portions 61a and 61b that become the fillet surfaces of the substrate do not have the insulating resin 4 and the conductive layer on the capacitor element connection surface, but only the conductive layer (second conductive layer) on the capacitor mounting electrode surface. Other parts are the same as those in the first embodiment. A cross-sectional view of the produced solid electrolytic capacitor is shown in FIG.

Example 4
In Example 2, referring to FIG. 5, the sleeper 3 and the sleeper anode connection part 5 were connected by the conductive adhesive 10, but in this example, they were connected by a laser. Others are the same as in the second embodiment.

  Since the sleeper anode connecting portion 5 of the substrate is plated with Au, it is difficult to absorb the energy of the laser, the temperature inside the substrate is difficult to rise, and the damage to the insulating resin 4 is reduced. The connection is not the alloying of the sleeper 3 and the sleeper anode connection part 5 of the substrate, but a part of the sleeper 3 is melted by a laser, and it flows and hardens on the interface between the sleeper 3 and the sleeper anode connection part 5 of the substrate and on the upper surface of the substrate. Connected with. Further, in this embodiment, since the Cu layer (conductive portion) of the substrate is thicker than in the first embodiment, the thermal diffusibility is good and the influence on the insulating resin 4 is small.

  Since this portion can be connected with a laser, the amount of the conductive adhesive 10 used is reduced by the amount of connection between the sleeper 3 and the sleeper anode connection portion 5 of the substrate, and the manufacturing speed is greatly improved.

(Comparative Example 1)
The details of the manufacturing method in this comparative example are obtained by improving the technique disclosed in Patent Document 1. FIG. 8 is an internal perspective view after the resin sheathing, and FIG. 9 is a cross-sectional view cut into product dimensions at the alternate long and short dash lines 81a and 81b. 9A is a side view of the anode side, FIG. 9B is a side view of the cathode side, and FIG. 9C is along the line BB in FIGS. 9A and 9B. It is sectional drawing. Although not described in Patent Document 1, the fillet surfaces 12 and 13 having good solder wettability are usually formed by plating the cut surfaces of the lead frames 82 and 83. In this comparative example, Sn plating treatment was performed.

(Comparative Example 2)
Details of the manufacturing method in this comparative example are disclosed in Patent Document 3. FIG. 10 is an internal perspective view after the resin exterior, and the lead frames 82 and 83 are processed into a concave shape. When the lead frames 82 and 83 are cut along the one-dot chain line portions 101a and 101b in FIG. Thus, the fillet surfaces 102 and 103 of the anode and the cathode are formed, respectively. FIG. 11 shows a view after cutting into product dimensions. 11A is a side view of the anode side, FIG. 11B is a side view of the cathode side, and FIG. 11C is along the line CC in FIGS. 11A and 11B. It is sectional drawing. In this comparative example, the shape of the recess was a rectangular parallelepiped, and the inside was subjected to Sn plating.

  Table 1 shows the number of fillet appearance defects when 100 bottom surface electrode type solid electrolytic capacitors were produced by the methods of Examples 1 to 3 and Comparative Examples 1 and 2 of the present invention, and a moisture resistance test as a reliability test. The number of occurrences of defects was shown. Appearance defects were defined as those in which the size of the anode fillet and cathode fillet was 2/3 or less of the design area. In the moisture resistance leaving test, an ESR of 1.5 times the initial value was regarded as defective.

  As shown in Table 1, there were no appearance defects in Examples 1 to 3 and Comparative Example 1, but in Comparative Example 2, four occurred. This is probably because, in Comparative Example 2, when the fillet surface is cut, very high positional accuracy is required, and the strength of the concave portions of the lead frames 104 and 105 that become the fillet surfaces 102 and 103 is weak. .

  In the moisture resistance test (65 ° C., 95% RH, 1000 hr), there were no defects in Examples 1 to 3 and Comparative Example 2, but three defects occurred in Comparative Example 1 in which the fillet surface was plated after cutting into product dimensions. did. This result indicates that application to the plating solution causes a decrease in reliability.

  Further, compared to the first embodiment, the thickness of the fillet forming portion can be reduced by 40 μm in the second embodiment and 160 μm in the third embodiment, and the volume efficiency can be improved.

  As described above, the bottom electrode type solid electrolytic capacitor fabricated according to the present invention has a fillet surface portion after resin coating as in Comparative Example 1 (corresponding to Patent Document 1), as compared with the conventional bottom electrode type solid electrolytic capacitor. There is no need for plating, which can improve product characteristic deterioration, productivity reduction and cost increase due to fillet surface formation.

  Further, in Comparative Example 2 (corresponding to Patent Document 3) in which a recess is formed in the electrode terminal, a plating treatment surface is provided therein, and the fillet surface is exposed on the side surface of the bottom electrode type solid electrolytic capacitor by cutting it. If the accuracy of cutting the concave portion by dicing is not sufficient, the fillet surface is highly likely to be scraped. However, in the present invention, the substrate is bent after cutting to form the fillet surface, so that there is no fear of scraping and it is difficult for defects to occur. This has a great advantage when the bottom electrode type solid electrolytic capacitor is downsized.

  As mentioned above, although the Example of this invention was described, this invention is not limited to this Example, Even if there is a design change of the range which does not deviate from the summary of this invention, it is included in this invention. That is, it goes without saying that various modifications and corrections that can be made by those skilled in the art are included. For example, in the above example, a capacitor element was produced using an anode lead made of a valve metal and a porous sintered body obtained by pressing and vacuum-sintering powder, but a plate-like or foil-like valve metal was used. It is obvious that a capacitor element may be manufactured using a porous body whose surface is enlarged by etching.

The solid electrolytic capacitor which concerns on embodiment and Example 1 of this invention is shown, Fig.1 (a) is a side view of an anode side end surface, FIG.1 (b) followed the AA line of Fig.1 (a). Sectional drawing. The top view which shows the pattern of the electroconductive part of the capacitor | condenser element connection surface in the board | substrate which concerns on embodiment and Example 1 of this invention. The bottom view which shows the pattern of the electroconductive part in the board | substrate which concerns on embodiment and Example 1 of this invention. The figure which shows the solid electrolytic capacitor manufacturing process after the capacitor | condenser element which concerns on the Example of this invention, and board | substrate connection. Sectional drawing of the solid electrolytic capacitor of Example 2. FIG. 6 is a plan view showing a capacitor element connection surface of a substrate used in Example 3. FIG. Sectional drawing of the solid electrolytic capacitor of Example 3. FIG. The internal perspective figure after the resin exterior of the solid electrolytic capacitor of a prior art example and the comparative example 1. FIG. FIGS. 9A and 9B are views after cutting the solid electrolytic capacitors of the conventional example and the comparative example 1, in which FIG. 9A is a side view on the anode side, FIG. 9B is a side view on the cathode side, and FIG. Sectional drawing along the BB line of (a) and FIG.9 (b). The internal perspective figure after the resin exterior of the solid electrolytic capacitor of a prior art example and the comparative example 2. FIG. FIGS. 11A and 11B are views after cutting into product dimensions of the solid electrolytic capacitors of the conventional example and the comparative example 2, FIG. 11A is a side view on the anode side, FIG. 11B is a side view on the cathode side, and FIG. These are sectional drawings along CC line of Drawing 11 (a) and Drawing 11 (b).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode lead wire 3 Sleeper 4 Insulating resin 5 Sleeper anode connection part 6 Capacitor element cathode connection part 7 Capacitor mounting surface anode 8 Capacitor mounting surface cathode 9 Via 10 Conductive adhesive 11 Exterior resin 12, 13, 102, 103 fillet surface 21, 81a, 81b, 101a, 101b alternate long and short dash line portion 22 alternate long and two short dashes line portion 23 broken line portion 51 substrate 61a, 61b portions 82, 83, 104, 105 which become fillet surfaces lead frame 84 insulating adhesive

Claims (3)

A capacitor element in which a dielectric oxide film is formed on the surface of a porous valve action metal body serving as an anode and a cathode layer including a solid electrolyte layer is formed on the dielectric oxide film,
A first conductive layer facing the capacitor element is formed on one of the two main surfaces of the plate-like insulating resin layer, and a second conductive layer as a mounting terminal is formed on the other, and the first and second A conductive layer is disposed on a substrate formed by electrical connection,
In the solid electrolytic capacitor in which the outer periphery of the capacitor element is resin-coated with a part of the substrate,
A solid electrolytic capacitor, wherein a portion of the substrate not covered with resin is bent along a side surface of the outer resin.   The solid electrolytic capacitor according to claim 1, wherein a thickness of the first conductive layer is thicker than that of the second conductive layer.   2. The solid electrolytic capacitor according to claim 1, wherein only the second conductive layer is formed on a portion of the substrate that is bent along the side surface of the exterior resin.

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