DE2734100A1 - Wet tantalum capacitors - using aq. electrolyte contg. perchloric and sulphuric acids to reduce residual current and loss factor - Google Patents

Abstract

The anode is made from sintered Ta powder and has a di-electric oxide coating formed electrochemically; and the cathode is formed by a liq. electrolyte, which is an aq. soln. (I) of HClO4 in a fine silver case coated internally with platinum sponge or mohr. (I) is pref. 40% HClO4 plus H2SO4; and is esp. an aq. soln. contg. (by wt.) 24.6% HClO4 plus 11.7% H2SO4 and also 0.5-3% vanadyl sulphate VOSO4; (I) may also contain H3PO4. The provides a single electrolyte (I) for wet Ta capacitors with nominal voltage up to 125 V, low residual currents, low loss factors, low impedance and a low temp. coefft. of specific conductivity.

Description

Electric condenser

The invention relates to an electrolytic capacitor whose anode is made of a sintered body made of tantalum powder and with an electrochemically generated, serving as a dielectric, oxide layer is provided, the cathode of which is through a liquid electrolyte is formed, and the in one on the inside with platinum sponge (Platinum black) covered fine silver case is built in.

Such capacitors, generally called wet sintered tantalum capacitors are characterized by the fact that they are different from all electrolytic capacitors have the lowest residual currents. They are available for nominal voltages up to 125 V.

It is because of the automation and rationalization required nowadays of manufacturing processes desirable if these capacitors for different Nominal voltage ranges are manufactured with one and the same electrolyte if possible can.

The object of the invention is therefore to provide an operating electrolyte for wet Indicate tantalum sintered capacitors, which are up to nominal tensions can be used up to 125 V and is also characterized by a low temperature coefficient its specific conductivity. Furthermore, the operating electrolyte should low residual currents, low loss factors and low impedance values in the finished capacitor.

According to the invention, this object is achieved in that the electrolyte consists of an aqueous solution of perchloric acid.

According to further developments of the invention, the electrolyte additionally contains Sulfuric and / or phosphoric acid and optionally has an addition of 0.5 to 3% by weight of vanadyl suliate aui.

The advantages of the operating electrolytes according to the invention are illustrated of the exemplary embodiments explained.

Embodiments 1 to 4 sintered tantalum electrolytic capacitors of Nominal data 25 / uF / 125 V were soaked with operating electrolytes according to the invention. For comparison, the values of electrolytic capacitors were measured with the conventional operating electrolyte made from 36% sulfuric acid.

In the following table 1 are the residual atmospheric values IR, the loss factors tan & and the impedance values Z of the capacitors mentioned are given, where in the exemplary embodiment 1 100 vol, 36 goat sulfuric acid, in the exemplary embodiment 2 100% by volume 40 goat perchloric acid, in exemplary embodiment 3 a mixture of 60 % By volume 40% perchloric acid (24.6% by weight) with 40% by volume 30.5% sulfuric acid (11.7% by weight) and in embodiment 4 a mixture of 60% by volume of 40% perchloric acid (24.6 wt. X) with 40% by volume of 30.5% strength sulfuric acid (11.7% by weight) with an additive of 1% by weight vanadyl sulate were used as operating electrolyte.

Table 1 IRRT: µA tan # 120Hz:% Z10 KHz: # RT -55 ° C -55 ° C 1. 36% H2SO4 1.50 1.04 8.9 3.35 2. 40% HC104 0.82 1.07 5.91 2.43 3. 24.6X HC104 + 0.79 1.05 5.77 2.39 11.7% H2S04 4. 24.6% HC104 + 0.87 1.04 6.59 2.58 11.7% H2S04 + 1X VoSO4 Table 1 shows the improvements that are achieved with the operating electrolyte according to the invention.

On the capacitors that are connected to the operating electrolyte according to the exemplary embodiments 1 and 2 were soaked, the conductivity and the spark voltage continued certainly. The results are shown in Table 2 below.

Table 2 #: ms / cm U: V -60 ° C -30 ° C +20 ° C 30 ° C 85 ° C 36% H2SO4 34 185 720 140 135 2. 40% HC104 62 240 710 150 150 The table shows that, on the one hand, an operating electrolyte according to the invention, which consists of 40% perchloric acid, has a higher spark voltage than the conventional operating electrolyte and, on the other hand, the new operating electrolyte has a higher conductivity at low temperatures, which is still not as strong is temperature-dependent as with the conventional electrolyte (low temperature coefficient of the specific electrical conductivity).

Embodiments 5 and 6 of sintered tantalum electrolytic capacitors the nominal data 1000 µF / 6 V became the loss factor tan & and the impedance Z determined at temperatures of -55 ° C.

The results are shown in Table 3 below.

Table 3 tan # 120 Hz: Z10 KHz: # 5. 36% H2SO4 1.13 2.03 6. 40% HC104 0.89 1.42 Table 3 shows that the operating electrolytes according to the invention can also be used for capacitors with low nominal voltages.

Overall, the operating electrolytes according to the invention stand out characterized in that they occur for all tantalum sintered electrolytic capacitors Nominal voltages can be used and in addition by cheap electrical Mark values with little temperature dependence.

6 claims

Claims (6)

Claims jl electrolytic capacitor whose anode is made from a sintered body consists of tantalum powder and an electrochemically generated dielectric serving, oxide layer is provided, the cathode of which is replaced by a liquid electrolyte is formed, and the inside with a platinum sponge (platinum black) Covered fine silver housing is built in, which is not shown e t that the electrolyte consists of an aqueous solution of perchloric acid. 2. Electrolytic capacitor according to claim 1, d a d u r c h g e k e n It is noted that the electrolyte consists of 40 units of perchloric acid. 3. electrolytic capacitor according to claim 1 or 2, d a d u r c h g It is not noted that the electrolyte also contains sulfuric acid. 4. electrolytic capacitor according to claim 3, d a d u r c h g e k e n It is noted that the electrolyte consists of a mixture of 60 vol% 40 pointer Perchloric acid and 40 vol% 30.5% sulfuric acid (24.6 wt., HC104 +11.7 wt. % H2SO4 in aqueous solution). 5. Electrolytic capacitor according to one or more of claims 1 to 4, d u r c h e k e n n n z e i c h n e t that the electrolyte is an additive from 0.5 to 3 oew. % Vanadyl sulfate. 6. Electrolytic capacitor according to one or more of claims 1 to 5, d u r c h e k e n n n z e i c h n e t that the electrolyte is an additive of phosphoric acid.