JPH09213570A - Chip type tantalum solid state electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of voids and unfilled parts, by specifying the distance between a partition line and the upper surface of a capacitor. SOLUTION: A tantalum capacitor element 6 wherein an anode external electrode 7A and a cathode external electrode 7B are fixed is accommodated in an upper metal mold wherein a distance 19 between a partition line 9 and the upper surface of a capacitor is set to be 0.1-0.3mm and a lower metal mold wherein a standoff part is eliminated. A sheath 22 is formed by using a transfer mold system wherein sheath resin composed of epoxy resin is injected from a resin gate of the partition line 9 surface. Thereby the fraction defective due to voids and unfilled parts which are contained in sheath resin can be reduced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a chip type tantalum solid electrolytic capacitor.

[0002]

2. Description of the Related Art In a chip type solid electrolytic capacitor, as shown in FIG. 3, an anode lead wire 1 is embedded in fine tantalum metal powder, and the fine tantalum metal powder is compression molded into pellets by pressing. Sinter to obtain porous pellet 2. Next, an oxide film, which is a dielectric, is formed on the surface of the porous pellet 2, the porous pellet having the oxide film formed is immersed in a manganese nitrate solution, and then the porous pellet 2 to which the manganese nitrate solution is adhered is formed. The manganese nitrate solution is decomposed by applying heat to deposit the manganese dioxide layer 3. After that, the operations of immersing the manganese nitrate solution in the porous pellets 2 → thermal decomposition of manganese nitrate → precipitation of the manganese dioxide layer 3 are repeated several times.

Next, a carbon paste is applied on the manganese dioxide layer 3 deposited on the surface of the porous pellet 2 and then dried to form a carbon layer 4. Next, a silver paste is applied to the surface of the carbon layer 4 to form a silver paste layer 5 to form a tantalum capacitor element 6. Then
After the anode lead wire 1 derived from the tantalum capacitor element 6 is cut while leaving a necessary portion, an external electrode 7 which is a lead frame made of nickel silver is resistance-welded 12 to the anode lead-out wire 1 by resistance welding 12. The anode external electrode is 7A. Next, the external electrode 7 which is a lead frame is soldered 13
And is used as a cathode external electrode 7B.

Next, as shown in FIG. 4, the anode external electrode 7
A, the tantalum capacitor element 6 to which the cathode external electrode 7B is attached is placed in the upper mold 14 and the lower mold 15, and is molded by transfer molding in which the exterior resin made of epoxy resin is injected from the resin gate 16 on the partition line 9. The exterior 8 is formed, and the lead frame, which is the external electrode 7, is formed along the exterior 8 to form a chip-type solid electrolytic capacitor.

[0005]

In the conventional chip type tantalum solid electrolytic capacitor, as shown in FIG. 3, after forming a tantalum capacitor element 6, an anode external electrode 7A and a cathode external electrode 7B are formed on the tantalum capacitor element 6. Install. Next, as shown in FIG. 4, this anode external electrode 7A
The line connecting the cathode external electrode 7B with the upper mold 4 and the lower mold is the partition line 9, and the mold outer casing 8 is formed by transfer molding with an outer resin made of epoxy resin.

Since the exterior resin made of this epoxy resin protects the tantalum capacitor element 6 from the influence of the force due to the thermal expansion of the exterior resin, it contains a large amount of filler having a size of 200 μm or less. The flow of the epoxy resin when performing the mold exterior 8 is bad. When the epoxy resin is injected into the mold from the resin gate 16 provided on the partition line 9, the space between the partition line 9 and the capacitor upper surface 10 has few obstacles and a small epoxy resin injection resistance, and the partition line. The flow rate of the epoxy resin and the flow velocity 17 are different in the part where there are many obstacles below 9 and the epoxy resin injection resistance is large, and the gas generated from the epoxy resin and the air contained in the epoxy resin go out of the mold. In the vicinity 18 where the epoxy resin merges, voids and unfilled parts often occur.

Particularly, in the conventional chip type solid electrolytic capacitor, the distance 11 between the partition line 9 and the upper surface 10 of the capacitor may be as large as 0.8 to 1.5 mm. There are many parts, and the occurrence rate of such voids and unfilled parts is 0.5 to 1.5% in the process, which is an obstacle to reducing defects.

[0008]

In order to solve the above problems, the present invention, as shown in FIG. 1, embeds an anode lead-out wire 1 in fine tantalum metal powder and sinters a pellet obtained by press-compressing a porous material. An oxide film is formed on the pellet 2, and a manganese dioxide layer 3, a carbon layer 4, and a silver paste layer 5 are formed on the surface of the oxide film to form a tantalum capacitor element 6. An anode external electrode 7A and a cathode external electrode 7B are attached to this tantalum capacitor element 6. Next, as shown in FIG. 2, after the anode external electrode 7A and the cathode external electrode 7B are attached to the tantalum capacitor element 6, the tantalum capacitor element 6 is put into the upper mold 20 and the lower mold 15, and is placed in this mold. Epoxy resin is injected from the resin gate 16 provided on the surface of the partition line 9.

However, as shown in FIG. 4, when the distance 11 between the partition line 9 and the upper surface 10 of the capacitor is 0.5 to 1.5 mm, which is the conventional value, when the upper mold 14 is used, the partition line 9 and the upper surface 10 of the capacitor are used. In the space with few obstacles and the space with many obstacles below the partition line 9, the epoxy resin flow rate and the flow velocity 17 are different, and voids and unfilled portions are generated. In order to prevent the occurrence of voids and unfilled portions, as shown in FIG. 2, by using an upper mold 20 having a distance 19 between the partition line 9 and the upper surface 10 of the capacitor of 0.1 to 0.3 mm, the partition is used. By making the injection resistance of the epoxy resin the same between the line 9 and the capacitor upper surface 10 and the space where the injection resistance of the epoxy resin is small and the space below the partition line 9 where there are many obstacles and where the resistance of the epoxy resin is large. The flow rate of the epoxy resin and the flow velocity 17 are the same in the space between the partition line 9 and the capacitor upper surface 10 and in the space below the partition line 9.

Therefore, since the gas generated from the epoxy resin and the air contained in the epoxy resin can be sufficiently discharged out of the mold, voids and the generation rate of the unfilled portion in the process are completely eliminated. As described above, in order to make the flow rate 17 and the flow velocity 17 of the epoxy resin in the space between the partition line 9 and the upper surface 10 of the capacitor and the space below the partition line 9 the same, the stand on the bottom surface of the capacitor shown in FIG. By eliminating the off 21 part and flattening the bottom surface of the capacitor as shown in FIG. 1, the occurrence rate of voids and unfilled parts in the process is further improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be demonstrated with reference to FIG. 1 by taking a chip type tantalum solid electrolytic capacitor as an example. A tantalum wire serving as the anode lead wire 1 is embedded in a tantalum fine powder having a mean particle diameter of 3 μm and a secondary particle diameter of about 100 μm, and the tantalum fine powder is press-compressed to form a tantalum pellet. And The tantalum pellets were sintered in a vacuum of 1500 to 1600 ° C., the porous pellets 2 were washed with pure water, then immersed in a 0.1% nitric acid solution, and the anodes derived from the porous pellets 2 were washed. Lead-out line 1
Then, a voltage is applied between 0.1% nitric acid solution and 0.1% nitric acid solution to perform chemical conversion to form an oxide film of tantalum pentoxide as a dielectric.

Next, the porous pellets 2 on which the oxide film has been formed are immersed in a manganese nitrate solution, and then the porous pellets 2 to which the manganese nitrate solution has adhered are heated to thermally decompose the manganese nitrate solution to form a manganese dioxide layer. Precipitate 3. The porous pellet 2 is dipped in a manganese nitrate solution, the thermal decomposition of manganese nitrate is performed, and the manganese dioxide layer 3 is deposited.
Repeat 0 times. Next, a carbon paste is applied to the surface of the manganese dioxide layer 3 deposited on the surface of the porous pellet 2 and then dried to form a carbon layer 4.

Then, a silver paste is applied to the surface of the carbon layer 4 and then dried to form a silver paste layer 5,
The tantalum capacitor element 6 is used. Next, after cutting the anode lead wire 1 derived from the tantalum capacitor element 6 while leaving a necessary portion, an external electrode 7 which is a lead frame made of nickel silver is resistance-welded 12 to the anode of the tantalum capacitor element 6. The anode external electrode 7A is attached to the tip of the lead wire 1. Then, the external electrode 7 which is a lead frame made of nickel silver is attached to the tantalum capacitor element 6 by soldering 13 to form a cathode external electrode 7B.

Next, the anode external electrode 7A and the cathode external electrode 7
As shown in FIG. 2, the tantalum capacitor element 6 to which B is attached has the upper mold 20 and the standoff 21 part so that the distance 19 between the partition line 9 and the capacitor upper surface 10 is 0.1 to 0.3 mm. An outer casing 22 is formed by a transfer molding method in which the outer casing resin made of epoxy resin is injected from the resin gate 16 on the surface of the partition line 9 into the lower mold 15. Then, the capacitor is taken out of the mold and the anode external electrode 7A and the cathode external electrode 7B are formed along the outer periphery of the outer package 22 to form a chip-type solid electrolytic capacitor.

[0015]

Since the chip type tantalum solid electrolytic capacitor of the present invention is manufactured as described above, it has the following unique effects. As shown in FIG. 5, the smaller the distance between the partition line of the chip-type tantalum solid electrolytic capacitor and the upper surface of the capacitor, the smaller the voids contained in the exterior resin and the unfilled defect rate. That is, in the conventional chip-type tantalum solid electrolytic capacitor, the distance between the partition line and the upper surface of the capacitor is 0.8 to 1.5 mm, and the void or unfilled defect rate during the process is 0.5 to 1.5%. there were. However, the defective rate was 0% by using the present invention.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the present invention.

FIG. 2 is a sectional view of the present invention.

FIG. 3 is a conventional sectional view.

FIG. 4 is a conventional sectional view.

FIG. 5 shows the relationship between the distance between the partition line and the upper surface of the capacitor and the defect rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Anode lead wire 2 ... Porous pellet 3 ... Manganese dioxide layer 4 ... Carbon layer 5 ... Silver paste layer 6 ... Tantalum capacitor element 7 ... External electrode 7A ... Anode external electrode 7B ... Cathode external electrode 8 ... Mold exterior 9 ... Partition Line 10 ... Capacitor upper surface 11 ... Distance between partition line and capacitor upper surface 12 ... Resistance welding 13 ... Soldering 14 ... Upper mold 15 ... Lower mold 16 ... Resin gate 17 ... Flow rate and flow velocity 18 ... Near confluence 19 ... Partition line Between the capacitor and the top surface of the capacitor 20 ... Upper mold 21 ... Standoff 22 ... Exterior

Claims (1)

[Claims] 1. A pellet obtained by embedding an anode lead wire in fine tantalum metal powder and press-compressing the fine tantalum metal powder, and sintering the pellet to obtain a porous pellet, and the surface of the porous pellet. In the chip-type tantalum solid electrolytic capacitor formed by forming an oxide film on the tantalum capacitor element having a manganese dioxide layer, a carbon layer, and a silver paste layer formed on the oxide film, and attaching external electrodes to the tantalum capacitor element. A chip type solid electrolytic capacitor, characterized in that the distance between the partition line and the upper surface of the capacitor is 0.1 to 0.3 mm.