JPH0722076B2 - Solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a solid electrolytic capacitor. More specifically, the present invention relates to improvement of heat resistance in an organic semiconductor solid electrolytic capacitor using a TCNQ complex salt as an electrolyte.

(B) Conventional Technology The inventors of the present application have already made various proposals regarding organic semiconductor solid electrolytic capacitors using TCNQ complex salts as electrolytes. That is, the solid electrolytic capacitor disclosed in JP-A-58-191414 (H01G 9/02) and the like, which uses a TCNQ complex salt with isoquinoline in which the N-position is substituted with an alkyl group, has particularly excellent high frequency characteristics. Therefore, it has been widely used for switching power supplies and the like, but in recent years, due to the need for downsizing of devices, this type of capacitor is also required to be used as a surface mounting component (chip component).

However, such TCNQ complex salt cannot withstand the thermal stress (usually 230 ° C.) when soldering, which is indispensable for surface mounting components, and causes characteristic deterioration such as a significant increase in leakage current. Therefore, as a means of improving the heat resistance of the above-mentioned TCNQ complex salt, the above-mentioned TCNQ
Various TCNQ complex salts having a melting point much higher than that of the complex salt (approximately 210 to 230 ° C) have been studied.

However, the high melting point TCNQ complex salts studied up to now are
Certainly the heat resistance improves but this TC after melting and cooling and solidification
The NQ complex salt is significantly inferior in conductivity to the conventional isoquinoline-based TCNQ complex salt, and has a serious drawback that the excellent high frequency characteristics, which is the greatest advantage of the solid electrolytic capacitor using the conventional TCNQ complex salt, are lost.

(C) Problems to be Solved by the Invention As described above, in the organic semiconductor solid electrolytic capacitor using the TCNQ complex salt, when trying to improve the solder heat resistance during surface mounting, there is a problem that the high frequency characteristics of the capacitor deteriorate. The objective is to solve both at the same time.

(D) Means for solving the problem When a high-melting TCNQ complex salt is used instead of the conventional isoquinoline-based TCNQ complex salt, the ESR (equivalent series resistance) is generally increased due to the decrease in the conductivity as an electrolyte, and the high frequency Deterioration of characteristics occurs. Therefore, in the present invention, two or more kinds of TCNQ complex salts having a high melting point and different cations are mixed, heated and melted, impregnated into a capacitor element and cooled and solidified to be used as an electrolyte. This is a solution to both the improvement in heat resistance and the improvement in high frequency characteristics of the electrolytic capacitor.

(E) Action ESR when high melting point TCNQ complex salts with two or more different cations are mixed, heated and melted, and cooled and solidified are TCNQ
It decreases to about 1/10 to 1/2 of the ESR value when the complex salt is used alone.
In other words, when the TCNQ complex salts having different cations are mixed and used, the conductivity is about 2 as compared with the case of the single TCNQ complex salt.
~ 10 times higher. In addition, when two or more TCNQ complex salts are mixed, it is presumed that the melting point of the TCNQ complex salt cooled and solidified after heating and melting is lower than that of a single case, but it is higher than the melting point of the conventional isoquinoline-based TCNQ complex salt, It has sufficient melting point and heat resistance to withstand the heat of reflow solder for surface mounting.

(F) Example The present invention will be described. FIG. 1 shows a capacitor element used in the present invention. First, a high-purity (99.99% or more) aluminum foil is roughened by a chemical treatment to perform a so-called etching treatment to increase the effective surface area. Next, an oxide film (a thin film of aluminum oxide) is electrochemically formed on the surface of the aluminum foil in the electrolytic solution (chemical conversion treatment). Next, the aluminum foil that has been subjected to etching treatment and chemical conversion treatment is used as an anode foil (1), and a manila paper is sandwiched between it and a counter cathode foil (2) as a separator (3) to form a cylindrical shape as shown in FIG. Roll up. The separator (3) interposed between the anode foil (1) and the cathode foil (2) thus formed with an oxide film on the aluminum foil and both electrode foils.
And are wound to form the capacitor element (6). Incidentally, (4) and (4 ') are aluminum leads, and (5) and (5') are lead wires.

Further, the capacitor element (6) is heat-treated to carbonize the manila paper constituting the separator (3) to reduce the density due to the fiber diameter reduction.

It should be noted that as a separator, a manila paper which has been heat-treated at a predetermined temperature and time (for example, 240 ° C., 40 minutes) and carbonized in advance is used, or a carbon non-woven fabric may be sandwiched between the anode foil and the cathode foil and wound. Good.

FIG. 2 is a sectional view of the capacitor element (6) housed in an aluminum case (7), and FIG. 3 is an external view thereof. A predetermined amount of various TCNQ complex salt (8) is put in the case (7), the aluminum case (7) is placed on a heated hot plate, and in this embodiment, the temperature of the case (7) is 310 to 315 ° C. Heat and melt the powdered TCNQ complex salt. On the other hand, the preheated capacitor element (6) is inserted into the aluminum case (7), and the molten mixture of TCNQ complex salt is added to the capacitor element (6).
And then immediately solidify by cooling. After that, a resin (9) that is difficult to react with the TCNQ complex salt is encapsulated and further molded with an epoxy resin or the like (10). (11) is a groove for the lead wire.

Next, Table 1 shows examples of TCNQ complex salts having a high melting point (approximately 230 ° C. or higher) in the present invention. Table 1 also shows the results of trial production of capacitors using these TCNQ complex salts by the melting method as described above. The complex salt symbol (I) is a conventional example. still,
The lutidine used for the synthesis of the complex salt symbols (A) (B) (H) in Table 1 is exactly 3.5-lutidine, and the phenylpyridine used for the synthesis of the symbols (C) (D) (E) is , To be precise, 4-phenyl pyridine. Furthermore, the ratings of the capacitors used in Table 1 and Table 2 are 25V, 0.68
μF, and the abbreviations used in these tables have the following meanings. That is, cap: Capacitance (nF), 120Hz tanδ: Loss tangent (%), 120Hz LC: Leakage current (μA / 1 minute later) ESR: Equivalent series resistance (mΩ), 100KHz △ cap: Electrostatic Capacitance change rate (%), 120Hz Table 2 shows the results of trial production of capacitors by the above-mentioned melting method by mixing equal amounts of the various TCNQ complex salts shown in Table 1, and reflow assuming heat during soldering during surface mounting. The test results are shown. This reflow test is to hold the capacitor at 160 ℃ for 2 minutes, and then to 230 ℃ at 30 ℃ in the reflow furnace.
It is a characteristic when held for a second.

The TCNQ complex salts may be mixed after synthesis and precipitation of the respective TCNQ complex salts, or may be mixed and precipitated during the synthesis reaction. Further, in the examples, only the case of mixing equal amounts is shown, but the basic effect of the present invention does not change at all even if the ratio is changed to 2: 1 or 3: 1.

Further, although the winding type capacitor of aluminum foil is shown as the capacitor element in the above-mentioned embodiment, a capacitor anode element obtained by press-molding or sintering a metal powder having a valve action such as aluminum, tantalum, niobium, Needless to say, the above-mentioned TCNQ complex salt of the present invention may be used as an electrolyte.

(G) Effect of the Invention According to the present invention, two or more kinds of TCNQ complex salts having different cations are mixed as described above, and the resulting mixture is heated and melted to impregnate a capacitor element, cooled and solidified, and used as an electrolyte.
It is possible to obtain a capacitor that can sufficiently withstand high temperature due to soldering during surface mounting while suppressing an increase in equivalent value series resistance (ESR) of the capacitor. That is, in the case of simply selecting a TCNQ complex salt having a high melting point for the sake of solder heat resistance during surface mounting, a conventional example, for example, a TCNQ complex salt with isoquinoline in which the N-position is substituted with an alkyl group is compared. ESR is about 7
~ 27 times, but according to the invention, the value is 2.4
It is possible to obtain a capacitor which is suppressed to about 6 times, and which can sufficiently withstand the high temperature at the time of reflow soldering for surface mounting.

[Brief description of drawings]

FIG. 1 is a perspective view of a capacitor element used in the present invention, FIG. 2 is a sectional view of a solid electrolytic capacitor of the present invention, and FIG. 3 is an external view thereof. (1) (2) ... positive, cathode foil, (3) ... separator,
(6) ... Capacitor element, (7) ... Aluminum case,
(8) ... Multiple TCNQ complex salts.

Claims (4)

[Claims] 1. A solid electrolytic capacitor, which comprises mixing two or more TCNQ complex salts having different cations, heating and melting the mixture, impregnating it as an electrolyte for a capacitor element, and then cooling and solidifying. 2. Two or more kinds of TCNQ complex salts are (a) a TCNQ complex salt with two molecules of lutidine in which the N-position is bound by substitution with a pentamethylene group or a hexylmethylene group, and (b) an N-position is a benzyl group or A TCNQ complex salt with isoquinoline substituted with a phenethyl group, (c) a TCNQ complex salt with phenylpyridine substituted with a hydrocarbon having 2 to 4 carbon atoms at the N position, any of the above (a), (b) and (c) Or a combination of two sets (that is, (a) (b), (a) (c), (b) (c))
Alternatively, the solid electrolytic capacitor according to claim 1, which is a combination of three sets (that is, (a) (b) (c)). 3. Two or more kinds of TCNQ complex salts are (a) a TCNQ complex salt with two molecules of lutidine in which the N position is bound by substitution with a pentamethylene group, and (b) the N position is substituted with an n-propyl group. The solid electrolytic capacitor according to claim 1, which is a combination of TCNQ complex salt with phenyl pyridine. 4. Two or more kinds of TCNQ complex salts are: (a) a TCNQ complex salt with two molecules of lutidine having N-positions substituted by a pentamethylene group, and (b) lutidine having N-positions substituted with a phenethyl group. TCNQ
The solid electrolytic capacitor according to claim 1, which is a combination of complex salts.