JP3067900B2 - Chip type tantalum solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an chip-type tantalum solid electrolytic capacitor and, more particularly, to a good chip type tantalum solid electrolytic capacitor of the heat resistance during soldering.

[0002]

2. Description of the Related Art FIG. 1 shows a chip type tantalum solid electrolytic capacitor.
A cross-sectional view of a state in which a resin exterior body made of a resin mold is formed around a capacitor element of a denser is shown, and the manufacturing process will be described step by step with reference to the figure.

[0003] First, a sintered pellet 1a is obtained by sintering and molding a tantalum powder as a valve metal powder. An anode lead 2 is implanted in the sintered pellet 1a.

Next, after forming an oxide film as a dielectric on the sintered pellet 1a, for example, manganese dioxide (M
A solid electrolyte 1b made of nO ₂ ) is formed.

[0005] Thereafter, the sintered pellet 1a is immersed in a carbon solution and then baked at a predetermined temperature to form a carbon layer 1 as a cathode extraction layer on the solid electrolyte 1b.
c, and a silver layer 1d is formed on the carbon layer 1c. That is, the carbon layer 1c and the silver layer 1d form a cathode layer.

After the capacitor element 1 is thus obtained, the anode lead 2 is connected to the anode terminal plate 3 of the lead frame.
a, and the cathode layer 1d is attached to the cathode terminal plate 3b of the lead frame via a conductive adhesive 4 such as adhesive silver.

Then, in a molding die (not shown),
A resin exterior body 5 made of, for example, epoxy resin is formed around the capacitor element 1 by a resin molding method.

After that, the anode terminal plate 3a and the cathode terminal plate 3b are cut into a predetermined length, and they are bent along the resin outer package 5.

[0009]

Although a chip-type tantalum solid electrolytic capacitor that can be surface-mounted is manufactured as described above, the resin conventionally used for the resin outer casing 5 has a large coefficient of thermal expansion. 4 of tantalum metal
The value is about double. Incidentally, the average linear expansion coefficient of tantalum metal is 0.66 × 10 ⁻⁵ 1 / ° C.

Therefore, when the capacitor element 1 is exposed to a high temperature during soldering, stress is applied to the capacitor element 1 due to the difference in the coefficient of thermal expansion, which causes defects in the solid electrolyte 1b and the dielectric film, thereby deteriorating the characteristics. was there.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional disadvantages, and its structural feature is that a capacitor element 1 mainly composed of a sintered pellet 1a of valve metal powder is used. An anode terminal plate 3 of a lead frame is provided on the anode lead 2 and the cathode layer 1d of the capacitor element 1.
a and the negative electrode terminal plate 3b are attached to each other, and the chip type tantalum solid electrolytic capacitor having the resin outer case 5 formed of a resin mold around the capacitor element 1 has a coefficient of linear expansion. Is 1.6
× 10 ⁻⁵ 1 / ° C. or less. By the way, the linear expansion coefficient of the resin exterior body 5
Is less than 0.8 × 10 ⁻⁵ 1 / ° C.,
When the molding of the resin exterior body 5 is completed by
The degree of shrinkage of the body 5 is small, and the package is difficult to release.
When the mold is released, a load is applied to the entire package,
Adversely affects the capacitor element 1 of the
It is not preferable because it causes a defect.

In this case, the low stress resin is preferably an epoxy resin. Further, by containing the filler in an amount of preferably 78 to 82 vol%, the linear expansion coefficient can be reduced to a desired value.

[0013]

The resin outer casing 5 is made of a low-stress resin, and its thermal expansion coefficient is not so different from that of the capacitor element 1. Therefore, even if it is exposed to a high temperature at the time of soldering, until the solid electrolyte or the dielectric film has defects. And the capacitor element is effectively protected.

[0014]

EXAMPLES Examples of the present invention will be described below along with comparative examples.

<< Embodiment 1 >> A capacitor element made of tantalum having a rating of 4 V and 22 μF is used, and its anode lead is welded to the anode terminal plate of the lead frame, and the cathode layer is bonded to the cathode terminal plate of the lead frame via adhesive silver. Installed. Then, it is set in a molding die, and the die temperature 160
C., resin injection pressure 40 kgf / square cm, resin molding time 150 seconds, epoxy resin K manufactured by Shin-Etsu Chemical Co., Ltd.
Using MC-180 (linear expansion coefficient 1.3 × 10 ⁻⁵ 1 / ° C.), a resin exterior body having a width of 1.94 mm, a height of 1.2 mm and a depth of 0.94 mm was formed around the capacitor element. After that, it is aged and inspected, and 960 good
When a solder heat resistance test was performed on the 0 pieces by dipping them in a 260 ° C. solder bath for 10 seconds, the number of defective leakage current characteristics was 0.

<< Embodiment 2 >> A capacitor element made of tantalum having a rating of 4 V and 22 μF was used, and its anode lead was welded to the anode terminal plate of the lead frame, and the cathode layer was bonded to the cathode terminal plate of the lead frame via adhesive silver. Installed. Then, it is set in a molding die, and the die temperature 160
C., resin injection pressure 40 kgf / square cm, resin molding time 150 seconds, epoxy resin ET6 manufactured by Risho Kogyo
1.94 mm width and 1.2 m height around the capacitor element using 050 (linear expansion coefficient 1.6 × 10 ⁻⁵ 1 / ° C.)
A resin exterior body having a m and a depth of 0.94 mm was formed. Thereafter, aging was performed, and an inspection was performed. A solder heat resistance test in which 9600 non-defective products were immersed in a 260 ° C. solder bath for 10 seconds was performed, and the number of defective leakage current characteristics was 1.

COMPARATIVE EXAMPLE 1 A capacitor element made of tantalum having a rating of 4 V and 22 μF was used, and its anode lead was welded to the anode terminal plate of the lead frame, and the cathode layer was bonded to the cathode terminal plate of the lead frame via adhesive silver. Installed. Then, it is set in a molding die, and the die temperature 160
C., resin injection pressure 40 kgf / square cm, resin molding time 150 seconds, epoxy resin K manufactured by Shin-Etsu Chemical Co., Ltd.
1. Using a MC103 (linear expansion coefficient 2.2 × 10 ⁻⁵ 1 / ° C.), a width of 1.94 mm and a height of 1.94 mm around the capacitor element.
A resin exterior body having a thickness of 2 mm and a depth of 0.94 mm was formed.
Thereafter, aging and inspection were performed, and 9600 non-defective products were subjected to a solder heat resistance test in which they were immersed in a 260 ° C. solder bath for 10 seconds.
Was individual.

Comparative Example 2 A capacitor element made of tantalum having a rating of 4 V and 22 μF was used, and its anode lead was welded to the anode terminal plate of the lead frame, and the cathode layer was bonded to the cathode terminal plate of the lead frame via adhesive silver. Installed. Then, it is set in a molding die, and the die temperature 160
C., resin injection pressure 40 kgf11 / square cm, resin molding time 150 seconds, epoxy resin EMC-300L manufactured by Nippon Steel Chemical Co., Ltd. (linear expansion coefficient 1.8 × 10 ⁻⁵ 1 /
° C) around the capacitor element using a width of 1.94 mm,
A resin exterior body having a height of 1.2 mm and a depth of 0.94 mm was formed. After that, it is aged and inspected, and 9
When a solder heat resistance test was conducted by dipping 600 pieces in a 260 ° C. solder bath for 10 seconds, the number of defective leakage current characteristics was 3 pieces.

As described above, according to the present invention, defective heat resistance during soldering is reduced. For reference, the above Examples 1 and 2
Table 1 shows the comparison results of Comparative Example 2 and Comparative Examples 1 and 2.

[0020]

[Table 1]

[0021]

As described above, according to the present invention,
By using a low-stress resin with a small coefficient of thermal expansion for the resin outer casing formed around the capacitor element, even if exposed to the high temperature during soldering, the solid electrolyte and dielectric film can reach defects. Chip type with no heat resistance
A tantalum solid electrolytic capacitor is provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a chip-type tantalum solid electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitor element 1a Sintered pellet 1b Solid electrolyte 1c Carbon layer 1d Silver layer 2 Anode lead 3a Anode terminal board 3b Cathode terminal board 4 Conductive adhesive 5 Resin exterior

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/08

Claims (3)

(57) [Claims] An anode terminal plate and a cathode terminal plate of a lead frame are attached to an anode lead and a cathode layer of the capacitor element, respectively. In a chip type tantalum solid electrolytic capacitor provided with a resin outer casing made of a resin mold around the capacitor element, the resin outer casing has a linear expansion coefficient of 1.6 × 10 ^{−5 /0.8°} C. or less . A chip-type tantalum solid electrolytic capacitor comprising a low-stress resin in a range of × 10 ⁻⁵ 1 / ° C. or more . 2. The chip type tantalum solid electrolytic capacitor according to claim 1, wherein said low stress resin is an epoxy resin. 3. The low stress resin has a filler of 78-82.
The chip-type tantalum solid electrolytic capacitor according to claim 1, wherein the content of the tantalum solid electrolytic capacitor is 1 vol%.