JPH0314040Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] This invention relates to solid electrolytic capacitors, and is particularly concerned with problems caused by the leakage of solder material connecting the external lead member to the electrode lead layer of the capacitor element during mounting on a printed circuit board. This invention relates to a structure for preventing characteristic deterioration.

[Prior art] Generally, this type of solid electrolytic capacitor is
As shown in the figure, a metal wire having a valve action is attached in advance to a capacitor element A which is formed by press-molding metal powder having a valve action into a cylindrical shape and sintering the anode lead B.
A first external lead member C is welded to this anode lead B, and a second external lead member D is formed on the circumferential surface of the capacitor element A via an oxide layer, a semiconductor layer, and a graphite layer. The capacitor element A is connected to the electrode lead layer E with a solder member F, and the entire circumferential surface of the capacitor element A is covered with a resin material G.

By the way, this capacitor is mounted on a printed board H, for example, as shown in FIG. 260℃
The printed conductor is soldered by immersing it in a molten solder tank K for about 10 seconds at a controlled temperature.

However, the first and second external lead members C,
D is usually composed of iron or a core wire mainly composed of iron coated with copper, and since the amount of copper used is as much as 30% by weight, the first and second external lead members are When C and D are immersed in the molten solder tank K, the capacitor element A is immersed in the molten solder tank K.
The heat conducted through the second external lead members C and D heats it to a high temperature in a short time. As a result, the solder member F on the circumferential surface of the capacitor element A becomes molten, and the solder layer plated on the surface of the second external lead member D also becomes molten. For this reason, the solder member F flows out from the resin material G along the second external lead member D, and as a result, the second external lead member D is electrically opened to the electrode lead layer E. The capacitor cannot function as a capacitor.

[Problems to be solved by the invention] Various proposals have been made to solve these problems. For example, in Japanese Patent Publication No. 59-36817, the outer circumferential surface of the solder member connecting the second external lead member to the electrode lead layer of the capacitor element is coated with metal powder, such as graphite powder, or resin, which has a higher melting point than the solder member. A solid electrolytic capacitor coated with a conductive member including the present invention is disclosed.

According to the conventional capacitor improved in this way, the solder material that solders the second external lead member to the electrode lead layer completely flows out of the resin material when mounted on a printed board, and the second external lead member is completely leaked out of the resin material. Even if the external lead member and the electrode lead layer of No. 2 are mechanically opened, they are locally electrically connected by the conductive member, and as a result, electrical open defects between the two can be completely eliminated. be.

However, when graphite powder is used as the metal powder for the conductive member, it is possible to prevent open defects as well as to minimize the impact on the cost of the capacitor. Dielectric loss (tanδ) tends to increase due to the fact that Aite powder has a higher resistivity than solder materials and the electrical connection by conductive materials when solder flows out is localized. This becomes noticeable when using graphite powder with a specific resistance of about 2×10 ^-1 to 3×10 ² Ω・cm, for example.
For 35V0.1μF products, before mounting on a printed board
Although tan δ (1KHz) is low at 1 to 2%, after implementation, it sometimes increases to 7 to 8%, which can be a problem depending on the application, such as audio equipment.

Therefore, the purpose of the present invention is to use a simple configuration to suppress the dielectric loss characteristics to a level that does not cause any practical problems even if the solder material connecting the second external lead member to the electrode extraction layer leaks out. Our objective is to provide solid electrolytic capacitors.

[Means for solving the problem] Therefore, in order to achieve the above-mentioned purpose, the present proposal takes the following measures:
An electrode lead layer is formed on the circumferential surface of a capacitor element made of metal powder with a valve action, from which an anode lead made of a metal wire with a valve action is derived, via an oxide layer, a semiconductor layer, and a graphite layer. Then, a first external lead member is welded to the anode lead of this capacitor element, and a second external lead member is soldered to the electrode lead layer,
In the case where the entire circumferential surface of the capacitor element is covered with a resin material, the second external lead member is soldered to the electrode lead layer portion of only a portion of the non-lead side of the anode lead of the capacitor element, and the solder member is The melting point is higher than that of the solder material, and the specific resistance is 2.
It is coated with a conductive material of ×10 ⁻¹ to 3×10 ² Ω·cm.

[Function] According to this invention, the second external lead member is soldered to the electrode lead layer portion of only a portion of the non-output side of the anode lead of the capacitor element, and the second external lead member is soldered to the non-bonded portion of the solder member as well as the solder member. The upper one has a higher melting point than the solder material and a specific resistance of 2×
It is coated with a conductive material having a resistance of 10 ^-1 to 3×10 ² Ω・cm. Therefore, even if all the solder material were to flow out during mounting on a printed board, the second external lead member would not be connected to the electrode. In the non-bonded part of the solder member adjacent to the soldered part to the lead-out layer, the electrode lead-out layer or the non-formed part of the electrode lead-out layer (graphite layer) is directly coated with the conductive member without using the solder member. Since the electrical connection is reliable and overall, for example, the specific resistance is between 2×10 ^-1 and 3×10 ²
Even if a conductive member made of graphite powder or the like having a relatively large Ω·cm is used, deterioration of dielectric loss characteristics can be suppressed to a level that does not cause any practical problems.

In addition, as a conductive member, the specific resistance is 2 × 10 ^-1 ~ 3 ×
Since a member made of graphite powder or the like having a relatively large resistance of 10 ² Ω·cm can be used, an inexpensive solid electrolytic capacitor can be provided.

[Example] Next, an example of the present invention will be described with reference to FIG.

In the figure, reference numeral 1 denotes a capacitor element made by pressure-forming metal powder with valve action into a cylindrical shape and sintering it. The wire is installed as an anode lead 2. Incidentally, the anode lead 2 can also be led out by welding to the circumferential surface of the capacitor element 1. An oxide layer, a semiconductor layer, and a graphite layer are sequentially formed on this capacitor element 1, and an electrode is made of a conductive material with excellent solderability on a part of the non-extracting side of the anode lead 2 on the circumferential surface of the capacitor element 1. A pull-out layer 3 is formed.
Note that the electrode lead layer 3 can also be formed on all the circumferential surfaces of the anode lead 2 except for the circumferential surface on the lead-out side.
On the other hand, an L-shaped first external lead member 4 is welded to the anode lead 2 of the capacitor element 1, and a straight second external lead member 5 is welded to the electrode lead layer 3 at its tip 5a. They are connected by a solder member 6 in a state where they are in contact with or in close proximity to each other. Then, the portion where the electrode lead layer 3 is not formed in the capacitor element 1 and the solder member 6
Above is a conductive member having a melting point higher than that of the solder member and having a specific resistance of 2×10 ^-1 to 3×10 ² Ω·cm so as to be electrically connected to the second external lead member 5. 7 is formed. The entire circumferential surface of the capacitor element 1 is made of resin material 8.
covered with. In addition to the molding method, the packaging can also be performed by a dipping method or the like.

Next, a method for manufacturing this capacitor will be explained with reference to FIGS. 2 to 5. First, as shown in Fig. 2, tantalum powder (metal powder with valve action) is pressure-molded into a cylindrical shape and sintered to form a capacitor element 1, and an anode made of tantalum wire is placed in the center of the capacitor element 1. Plant lead 2. This capacitor element 1 includes an oxide layer, a semiconductor layer,
Graphite layers are formed in sequence. Next, as shown in FIG. 3, the capacitor element 1 is supported so that the anode lead 2 is located above and the non-lead side is located below, and only the lower end of the capacitor element 1 is covered with the conductive material liquid 3 ₀ . After immersing it in and pulling it up,
By drying, the electrode lead layer 3 is formed. This electrode extraction layer 3 has a specific resistance of, for example, 1×
It is made of a conductive material with a resistance of 10 ^-4 Ω・cm or less and excellent wettability to solder materials. As the above-mentioned conductive member liquid ₃₀ , for example, a silver paste composed of silver powder, resin, and solvent, in which the ratio of silver powder to the total amount is set to 70% by weight, is suitable, but within a range where the wettability to the solder member is not impaired. It is also possible to replace a part of the silver powder with tin powder, nickel powder, copper powder, etc.

Next, as shown in FIG. 4, connect L to the anode lead 2.
After the straight-shaped first external lead member 4 is welded, a straight-shaped second external lead member 5 is arranged in parallel to the capacitor element 1 so that the tip portion 5 a is in contact with the electrode extraction layer 3 . In this state, the second external lead member 5 is soldered to the electrode lead layer 3 by dipping the lower end of the capacitor element 1 into a molten solder bath. In addition, since the graphite layer is exposed in the part of the capacitor element 1 where the electrode lead layer 3 is not formed, when the capacitor element 1 is placed in a molten solder bath, not only the part where the electrode lead layer 3 is formed but also the part where the electrode lead layer 3 is not formed is exposed. Even if the second external lead member 5 is partially immersed, the second external lead member 5 is soldered only at the portion where the electrode lead layer 3 is formed.

Next, as shown in FIG. 5, this capacitor element 1 is immersed in a conductive material liquid ₇₀ containing metal powder with a melting point higher than that of the solder material 6, taking care not to immerse the peripheral surface on the output side of the anode lead 2, and then pulled up. After that, by drying, the portion where the electrode lead layer 3 is not formed and the top of the solder member 6 are covered with the conductive member 7.
This conductive member has a higher melting point than the solder member, and its specific resistance is preferably 2×10 ^-1 to 3×10 ² Ω・
The conductive member liquid ₇₀ is composed of graphite powder, resin, and water. Here, it is desirable that the specific resistance of the conductive member be small, but it is difficult to find a material that is less than 2×10 ^-1 Ω・cm, has a high melting point, and is inexpensive ^;
For components exceeding cm, it is not possible to improve the deterioration of dielectric loss characteristics after solder flows out. Finally, the entire circumferential surface of the capacitor element 1 is coated with a resin material 8 to obtain the solid electrolytic capacitor shown in FIG. 1.

When the tanδ (1KHz) of the 35V 0.1μF tantalum solid electrolytic capacitor manufactured in this way was measured,
It was 1-2%. After this capacitor element was mounted on a printed board using the usual method (FIG. 7), the tan δ (1KHz) was measured and found to be 1 to 3%.

In the present invention, the shapes of the capacitor element and the external lead member can be changed as appropriate. Further, the electrode lead layer is preferably formed in a range of 30 to 70% of the length of the capacitor element, but it can also be formed in the peripheral surface portion excluding the lead-out side of the anode lead.

[Effects of the invention] As described above, according to the invention, even if all the solder material flows out of the resin material during mounting on a printed circuit board, the second external lead member can be attached to the soldered portion of the electrode lead layer. In the non-adhesive part of the solder member adjacent to the electrode lead layer or the non-formed part of the electrode lead layer (graphite layer), a layer having a melting point higher than that of the solder member and a specific resistance of 2 × 10 ^-1 to 3 × 10 ² is added. Ω・
Since the electrical connection is made directly, reliably, and overall by the conductive member that is cm without the use of solder members,
For example, even if a conductive member made of graphite powder or the like, which has a relatively large specific resistance of 2×10 ^-1 to 3×10 ² Ωcm, is used, the deterioration of the dielectric loss characteristics should be kept to a level that does not cause any practical problems. I can do it.

In addition, as a conductive member, the specific resistance is 2 × 10 ^-1 ~ 3 ×
Since a member made of graphite powder or the like having a relatively large resistance of 10 ² Ω·cm can be used, an inexpensive solid electrolytic capacitor can be provided.

[Brief explanation of the drawing]

Figure 1 is a side sectional view showing one embodiment of the present invention, Figure 2
5 to 5 are explanatory diagrams of the manufacturing method, in which FIG. 2 is a side sectional view of the capacitor element, FIG. 3 is a side sectional view showing the state of formation of the electrode lead layer, and FIG. 2 is a side sectional view showing how the external lead member is connected to the capacitor element, FIG. 5 is a side sectional view showing how it is covered with a conductive member, FIG. 6 is a side sectional view of the conventional example, and FIG. 7 is a printed board. FIG. In the figure, 1 is a capacitor element, 2 is an anode lead, 3 is an electrode lead layer, 4 is a first external lead member, 5 is a second external lead member, 6 is a solder member, 7 is a conductive member, and 8 is a resin It is a material.

Claims (1)

[Claims for Utility Model Registration] (1) An oxide layer, a semiconductor layer, An electrode lead layer is formed through the graphite layer, a first external lead member is welded to the anode lead of the capacitor element, a second external lead member is soldered to the electrode lead layer, and the capacitor element in which the entire circumferential surface of the capacitor element is covered with a resin material, the second external lead member is soldered to the electrode lead layer portion of only a portion of the non-output side of the anode lead of the capacitor element, and the solder member is not attached. The melting point is higher than that of the solder member, and the specific resistance is 2×10 ^-1 ~
A solid electrolytic capacitor characterized by being coated with a conductive material having a conductivity of 3×10 ² Ω・cm. (2) Utility model registration claim item (1) characterized in that the main component of the conductive member is graphite powder, and its specific resistance is 2×10 ^-1 to 3×10 ² Ωcm. Solid electrolytic capacitors described in . (3) The solid electrolytic capacitor according to claim (1) of the utility model registration, characterized in that the electrode lead layer is formed in a large area portion of the capacitor element or in a limited small area portion.