JP5358403B2 - Chip type solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a state, i.e. an open state, wherein connection resistance becomes infinite owing to an increase in ESR or a defect in electrical connection between a cathode layer and an internal cathode terminal 9 as cracking or peeling due to the warpage of the conversion substrate, caused by thermal stress occuring at a connection interface in the presence of stressing by thermal stress of resin or external direct stress. <P>SOLUTION: A chip-type solid electrolytic capacitor uses a cathode conductive adhesive 7, having a scratching hardness of 2B to 6B (in a pencil method) after a conductive adhesive is cured. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a chip-type solid electrolytic capacitor.

  FIG. 2 is a perspective view showing an example of a conventional chip-type solid electrolytic capacitor. For example, the chip-type solid electrolytic capacitor has the same configuration as the bottom electrode-type solid electrolytic capacitor described in Patent Document 1, and includes a capacitor element 1 and a chip. Conversion substrate 4 having an external anode terminal 5 and an external cathode terminal 6 for connecting an internal anode terminal 11 and an internal cathode terminal 9 that are connected to the capacitor element 1 and an external substrate within the solid electrolytic capacitor. The chip-type solid electrolytic capacitor provided with this is represented.

  Capacitor element 1 has a dielectric layer formed on a tantalum sintered body in which anode lead 2 is embedded in tantalum sintered body in advance, a solid electrolyte layer (such as manganese) is formed on the surface, and a graphite layer, It is made by sequentially coating silver layers.

  Next, the metal piece 3 made of iron, copper, nickel, or an alloy thereof is resistance-welded to the anode lead wire 2. Further, an anode conductive adhesive 8 such as an Ag paste containing a metal such as Ag is applied to the internal anode terminal 11 of the conversion substrate 4 to connect the metal pieces 3 and simultaneously an Ag paste containing a metal such as Ag. A cathode conductive adhesive 7 such as is applied to the internal cathode terminal 9, the cathode layer is connected, and heated and cured.

  Thereafter, the exterior resin 10 is molded, and if necessary, dicing is performed later to obtain a chip-type solid electrolytic capacitor.

  In the prior art, the cathode conductive adhesive 7 for connecting the cathode layer of the capacitor element 1 and the internal cathode terminal 9 places importance on connection strength and uses an organic binder such as epoxy resin or acrylic resin. . In addition, two types of Ag pastes containing epoxy resin and acrylic resin and fluorine-based elastomers with different elastic states for the purpose of giving connection strength and absorbing and mitigating thermal stress due to thermal history are connected to two connection parts. Techniques for applying separately are also proposed. (Patent Document 2)

JP 2008-258602 A JP 2006-186083 A

  However, the chip type solid electrolytic capacitor manufactured by the conventional technique as described above has the following problems.

  The first is a concern about cracks or peeling due to thermal stress or the like at the connection portion between the cathode layer of the capacitor element 1 and the internal cathode terminal 9. In general, the connection portion between the cathode layer and the internal cathode terminal 9 is required to have a connection strength enough to prevent peeling and dropping before the molding with the exterior resin 10 is completed, and to withstand the pressure during molding. However, when the cathode conductive adhesive 7 containing an epoxy resin or the like is used, the adhesive strength sufficiently satisfies the required value, but elastic deformation is difficult, and there is a trade-off relationship with product reliability. Met. In recent years, the heating temperature at the time of reflow tends to increase due to the improvement of productivity and the spread of lead-free solder. Stress is generated by thermal stress due to reflow or external direct stress, and in particular, warping due to thermal stress due to reflow of the conversion substrate 4 causes cracks or peeling at the connection interface, increasing ESR, and the cathode layer and internal cathode terminal. There is a concern that the connection resistance becomes infinite, that is, an open state occurs due to the electrical connection failure 9.

  The second is an elastic state that contains epoxy resin, acrylic resin, and fluoroelastomer for the purpose of giving the connection strength that is a trade-off relationship of conductive adhesive and alleviating thermal stress due to thermal history. When two different types of Ag paste are separately applied to two connecting portions, there is a problem that the work efficiency is lowered and the man-hours for quality control of each Ag paste are lowered in productivity. In addition, when two types of Ag paste with different elastic states are applied to two adjacent locations that are difficult to separate structurally, and the two types of Ag paste come into contact with each other due to pressure, etc., the connection strength of the contacted interface It is judged that confirmation is necessary.

  In general, tensile modulus is often used as an index to indicate the elastic state of relatively hard resins such as epoxy resins and acrylic resins, but conductive adhesives with rubber-like properties are processed into the shape required for measurement. In some cases, it was difficult to carry out the test. Then, it examined paying attention to scratch hardness (pencil hardness of a pencil method) as an index showing the elastic state of the conductive adhesive of the present invention.

  Therefore, the present invention provides a chip-type solid electrolytic capacitor capable of preventing an increase in ESR due to cracks and peeling at a connection interface under various stresses, and preventing an open state at a cathode connection portion and improving productivity. For this purpose, the numerical range of the scratch hardness (pencil hardness of the pencil method) of the conductive adhesive is optimized in relation to the above-mentioned specific effects and problems.

In order to solve the above problems, a chip-type solid electrolytic capacitor according to the present invention includes an anode body made of a valve metal from which an anode lead wire is derived, a dielectric layer formed on the surface of the anode body, and the dielectric A capacitor element having a cathode layer composed of an electrolyte layer, a graphite layer, and a silver layer sequentially formed on the layer, and a conversion substrate, and a metal connected to the anode lead wire on the upper surface of the conversion substrate It has an internal anode terminal connected to the piece by an anode conductive adhesive, and an internal cathode terminal connected to at least a part of one surface of the cathode layer by a cathode conductive adhesive . An external anode terminal and an external cathode terminal are formed as capacitor mounting electrode terminals, and the capacitor element and the conversion substrate are externally covered with an exterior resin with the external anode terminal and the external cathode terminal exposed. Mold A-up type solid electrolytic capacitor, scratching at JISK5600-5-4 after curing at least the cathode conductive adhesive hardness (pencil method) is characterized in that it is a 2B～6B.

  The chip-type solid electrolytic capacitor of the present invention is characterized in that at least one of the anode conductive adhesive and the binder of the cathode conductive adhesive is mainly composed of a fluorine-based elastomer or silicone.

  In the present invention, in order to solve the above-mentioned object, a conductive adhesive having a scratch hardness capable of relieving external stress is used at least as a cathode conductive adhesive for connecting the capacitor element and the internal cathode terminal. Therefore, it is possible to prevent cracks and peeling at the connection interface due to reflow heat and direct stress, for example, stress due to deviation of thermal expansion coefficient between the internal cathode terminal of the conversion board and the capacitor element, and productivity. It is possible to supply a chip type solid electrolytic capacitor capable of improving the above.

  Furthermore, the chip-type solid electrolytic capacitor of the present invention has both sufficient adhesive strength and an elastic state suitable for ensuring product reliability, and has durability against heating during reflow. As the agent, it is preferable to use a conductive adhesive mainly composed of a fluorine-based elastomer and silicone.

The perspective view which shows 1st embodiment, 2nd embodiment, and 3rd embodiment of the chip-type solid electrolytic capacitor by this invention. The perspective view which shows the chip-type solid electrolytic capacitor by a prior art. The figure which shows the change (thermal history: before and after reflow) of ESR by a thermal history. (The figure which shows the change of level 2 of Example 1 and a comparative example) The figure which shows the change of ESR according to the level of scratch hardness. (Example 1, changes before and after reflow)

  Embodiments of the present invention will be described with reference to the drawings. Incidentally, a part of FIG. 1 is hatched for easy understanding.

(First embodiment)
FIG. 1 is a perspective view showing a first embodiment of a chip-type solid electrolytic capacitor according to the present invention. The overall structure is the same as that of the prior art, and an anodic oxide film serving as a dielectric layer is formed on a tantalum sintered body in which the anode lead 2 is embedded in the tantalum sintered body in advance, and a solid made of manganese dioxide or the like on the surface. An electrolyte layer is formed, and a capacitor element 1 coated with a graphite layer and a silver layer as a cathode layer is prepared. Next, the metal piece 3 is resistance welded to the anode lead wire 2.

  The solid electrolyte layer may be formed by forming a layer of polypyrrole, polythiophene, or polyaniline.

  An anode conductive adhesive 8 containing epoxy or acrylic resin as a main component binder and containing a metal such as Ag is applied to the internal anode terminal 11 on the conversion substrate 4, and the metal piece 3 is connected. At the same time, the cathode layer is bonded to the internal cathode terminal 9 coated with a cathode conductive adhesive 7 containing a fluorine-based elastomer as a main component and containing a metal such as Ag, and is heated and cured together.

  Thereafter, molding is performed using the exterior resin 10, and dicing is performed later as necessary to obtain a chip-type solid electrolytic capacitor.

(Second embodiment)
Next, a second embodiment of the chip-type solid electrolytic capacitor according to the present invention will be described with reference to FIG. The entire structure is the same as that of the first embodiment, and an anodic oxide film serving as a dielectric layer is formed on a tantalum sintered body in which the anode lead wire 2 is previously embedded in the tantalum sintered body, and a solid electrolyte is formed on the surface thereof. A capacitor element 1 is formed by forming a layer (such as manganese) and coating it with a graphite layer and a silver layer as a cathode layer. Next, the metal piece 3 is resistance-welded to the anode lead wire 2.

  An anode conductive adhesive 8 containing epoxy or acrylic resin as a main component binder and containing a metal such as Ag is applied to the internal anode terminal 11 on the conversion substrate 4, and the metal piece 3 is connected. At the same time, the cathode layer is adhered to the internal cathode terminal 9 coated with the cathode conductive adhesive 7 containing a silicone resin as a main component and containing a metal such as Ag, and is heated and cured together.

  Thereafter, the exterior resin 10 is molded, and a chip-type solid electrolytic capacitor is obtained by performing dicing later if necessary.

(Third embodiment)
Subsequently, a third embodiment of the chip-type solid electrolytic capacitor according to the present invention will be described.

  Since the third embodiment is configured in the same manner as the first embodiment, descriptions other than the main part are omitted. The structure of the third embodiment will also be described with reference to FIG.

  In the third embodiment, the present invention is also applied to the connection between the internal anode terminal 11 and the metal piece 3. The internal anode terminal 11 on the conversion substrate 4 includes a fluorine-based elastomer as a main component binder, Ag. An electrically conductive anode conductive adhesive 8 containing a metal such as is applied, the metal piece 3 is connected, and the internal cathode terminal 9 is made of a fluorine elastomer as a main component binder, and a metal such as Ag is applied. The contained cathode conductive adhesive 7 is applied, the cathode layer is attached, and heated and cured.

  Thereafter, the exterior resin 10 is molded, and a chip-type solid electrolytic capacitor is obtained by performing dicing later if necessary.

  As a result of examining the scratch hardness of these conductive adhesives in detail, when the scratch hardness is in the range of 2B to 6B, the internal cathode terminal and the conductive adhesive due to the thermal stress caused by reflow that has occurred in the prior art. It has been found that cracks are prevented from occurring at the connecting interface of the agent, suppressing the rise of ESR and preventing the occurrence of open defects.

  Moreover, in said 1st to 3rd embodiment, regardless of the combination of the electroconductive adhesive which comprises the cathode conductive adhesive 7 and the anode conductive adhesive 8, the above-mentioned scratch hardness is 2B-6B. If it is within the range, the connection is made using not only the same type but also two types of conductive adhesive containing metal such as Ag with fluorine-based elastomer or silicone resin as the main component. It doesn't matter.

  Examples of the present invention and comparative examples will be described in detail below.

Example 1
A specific example of the chip-type solid electrolytic capacitor of the present invention will be described with reference to FIG. 1 used in the first embodiment.

  In Example 1, a plurality of conductive adhesives in which the scratch hardness after curing was changed to 6 levels between 1B and 7B were prepared, and the chip type using these conductive adhesives as the cathode conductive adhesive 7 100 solid electrolytic capacitors were produced. The shape of the chip-type solid electrolytic capacitor was a longitudinal dimension of 2.0 mm, a short dimension of 1.2 mm, and a thickness of 1.0 mm. A six-level conductive adhesive having a changed scratch hardness after curing was prepared by using a fluorine-based elastomer and adjusting the content of the fluorine-based elastomer in a range of 5 to 50 mass%.

  Next, the manufacturing process will be described. An anodic oxide film is formed on a tantalum sintered body in which an anode lead wire 2 made of a tantalum wire is previously embedded in the tantalum sintered body, a manganese dioxide solid electrolyte layer is formed on the surface, and a graphite layer, silver as a cathode layer Capacitor element 1 in which the layers were sequentially coated was prepared. Next, a metal piece 3 made of 42 alloy (Ni-42%, Fe-58%) was resistance welded to the anode lead wire 2.

  Thereafter, a conductive anode conductive adhesive 8 containing an epoxy resin as a main component binder and containing Ag is applied to the internal anode terminal 11 on the conversion substrate 4, and the metal piece 3 is connected. A cathode layer was connected to an internal cathode terminal 9 coated with a cathode conductive adhesive 7 containing Ag, using a 6-level fluoroelastomer having a changed scratch hardness after curing as a main component binder. The conductive adhesive was applied to the terminal pattern with a syringe. Thereafter, in order to complete the connection, it was cured by heating at 150 ° C. for 20 minutes.

  Next, molding was performed using an epoxy-based exterior resin 10 containing a glass filler, and dicing was performed using a diamond blade, thereby obtaining a chip-type solid electrolytic capacitor.

(Comparative example)
The same epoxy resin used in the prior art is used as a main component binder, and a conductive adhesive containing Ag is applied to the internal anode terminal 11 and the internal cathode terminal 9 on the conversion substrate 4, respectively. The metal piece 3 and the cathode layer were connected. Other manufacturing processes were carried out in the same manner as in the present invention.

  The scratch hardness of each level of conductive adhesive used in Example 1 with varying elasticity was measured according to JIS K5600-5-4. Specifically, these conductive adhesives were applied to an aluminum material for evaluation and then cured to measure the scratch hardness. In JISK5600-5-4, the scratch hardness is defined in the range of 6H to 6B (hard → soft), so that a softer one was determined using a 7B pencil.

  Each level n = 100 was processed in a reflow furnace at a peak temperature of 260 ° C. and a keep temperature of 250 ° C. for 10 seconds, and ESR was measured by a known method.

  Table 1 shows each level of Example 1 and the results of the comparative example.

※ＥＳＲ不良率：リフロー後のＥＳＲ不良率。
※モールド時不具合発生率：成型樹脂の外側へ導電性接着剤が流出等の発生率。
※ＥＳＲ不良率の判定：ＥＳＲの上昇率が１０％以上のものが１０％以上発生している場合は×とした。
※モールド時不具合発生率の判定：モールド時不具合の発生率が５％以上発生している場合は×とした。

* ESR failure rate: ESR failure rate after reflow.
* Mold failure rate: The rate at which the conductive adhesive flows out of the molding resin.
* Judgment of ESR defect rate: When the rate of increase of ESR is 10% or more, 10% or more occurs.
* Judgment of failure rate during molding: x is indicated when the failure rate during molding is 5% or more.

  From Table 1 above, in the scratch hardness after curing of the conductive adhesive, the scratch hardness 7B is too soft, and when molding with exterior resin, the conductive adhesive flows out, the internal element is poorly exposed and the leakage current is poor. Such problems occur. In the case of scratch hardness 1B, it is too hard to cause the same problem as that of a conventional conductive adhesive such as epoxy. Therefore, it can be seen that the scratch hardness is in the range of 2B to 6B and is effective for the above problem.

  Next, the improvement of ESR in Example 1 will be described with reference to the graph shown in FIG. This is a diagram comparing the level 2 of the present invention shown in Table 1, the prior art, and the change in ESR characteristics before and after the thermal history. For the conventional ESR, when thermal stress due to reflow is applied, a crack occurs at the connection interface between the internal cathode terminal and the conductive adhesive, the connection resistance at the connection interface increases, and the average value (AVE) of the ESR is greatly increased. To rise. In the present invention, since cracks can be prevented at the connection interface, an increase in connection resistance at the connection interface is suppressed, and an increase in the average value (AVE) of ESR is improved by about 36%.

  FIG. 4 is a graph showing the contents of Table 1, and shows the change in ESR before and after the reflow of the chip-type solid electrolytic capacitor according to the level of scratch hardness. This shows that the increase in ESR is suppressed in the range of scratch hardness of 2B to 6B, and the effect of the present invention is observed.

  In addition, the prevention of the reduction in work efficiency, which is the second problem of the present invention, is a process in which one type of conductive adhesive is applied to each of the internal cathode terminal and the internal anode terminal. Replacement frequency, increased production equipment downtime, and increased man-hours required for quality control of conductive adhesive.

(Example 2)
Next, a second embodiment of the chip-type solid electrolytic capacitor of the present invention will be described with reference to FIG.

  In Example 2, the content rate of silicone resin was adjusted in the range of 5-50 mass%, and the several conductive adhesive which made the scratch hardness after hardening 6 levels between 1B and 7B was prepared.

  A conductive anode conductive adhesive 8 containing epoxy resin as a main component binder is applied to the internal anode terminal 11 on the conversion substrate 4, and the metal piece 3 is connected to the internal anode terminal 11. A cathode layer was connected to an internal cathode terminal 9 coated with a cathode conductive adhesive 7 containing Ag, using a 6-level silicone resin having a changed scratch hardness as a main component binder. Other conditions and manufacturing steps were the same as in Example 1.

(Comparative example)
The comparative example of Example 2 was also manufactured under the same conditions and manufacturing process as the comparative example of Example 1.

  The measurement method for each measurement item is the same as that in the first embodiment.

  Table 2 shows each level of Example 2 and the results of the comparative example.

(Example 3)
Further, a third embodiment of the chip-type solid electrolytic capacitor of the present invention will be described with reference to FIG.

  In Example 3, not only the internal cathode terminal 9 but also the internal anode terminal 11 is composed of a fluorine-based elastomer as a main component, and a cathode conductive adhesive 7 containing Ag is used. 9 was connected. Other conditions were the same as in Example 1.

(Comparative example)
The comparative example of Example 3 was also produced under the same conditions and manufacturing process as the comparative example of Example 1.

  The measurement method for each measurement item is the same as that in the first embodiment.

  Table 3 shows each level of Example 3 and the results of the comparative example.

  As can be seen from the results of Tables 2 and 3, scratch hardness 2B to 6B after curing of the conductive adhesive constituting the cathode conductive adhesive 7 and the anode conductive adhesive 8 suppresses the increase in ESR. It can be seen that the effect of the present invention is observed.

  The embodiments of the present invention have been described above using the embodiments. However, the present invention is not limited to these embodiments, and the present invention is not limited to the scope of the present invention. Included in the invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode lead wire 3 Metal piece 4 Conversion board 5 External anode terminal 6 External cathode terminal 7 Cathode conductive adhesive 8 Anode conductive adhesive 9 Internal cathode terminal
10 Exterior resin 11 Internal anode terminal

Claims (2)

An anode body made of a valve metal from which an anode lead wire is derived, a dielectric layer formed on the surface of the anode body, an electrolyte layer, a graphite layer, and a silver layer sequentially formed on the dielectric layer A capacitor element having a cathode layer and a conversion substrate, and an upper surface of the conversion substrate, an internal anode terminal connected to the metal piece connected to the anode lead wire by an anode conductive adhesive , and a internal cathode terminal connected at the cathode electrode conductive adhesive to at least a portion of one surface of the cathode layer, on the lower surface, and the external anode terminal and the external cathode terminal as an electrode terminal capacitor mounting formation It is, the converted substrate and the capacitor element, wherein the exterior by external anode terminal and the external cathode terminal to expose the by exterior resin, a lower surface electrode type chip type solid electrolytic capacitor, at least the cathode conductive contact Chip type solid electrolytic capacitor agent characterized in that the scratch hardness degree of JISK5600-5-4 after curing is 2B～6B.   2. The chip-type solid electrolytic capacitor according to claim 1, wherein at least one of the anode conductive adhesive and the binder of the cathode conductive adhesive is mainly composed of a fluorine-based elastomer or silicone.

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