DE4029110A1 - Electrical capacitors contain as solid electrolyte - conductive polymer prepd. by repeatedly applying and polymerising 3,4-ethylene-di:oxy-thiophene with ferric toluene-p-sulphonate - Google Patents

Abstract

In prodn. of condensers consisting of (A) positive rectifier electrode with dielectric oxide layer; (B) negative electrode; (C) opt. sepg. films, and (D) conventional contacting, wherein conductive polymer (I) formed by polymerising a soln. of 3,4-ethylenedioxythiophen (II) and Fe(iii) tosylate (III) as electrolyte is applied on (A) or (C) is impregnated therewith, (I) is made by several consecutive polymerisation cycles from solns. applied repeatedly. ADVANTAGE - Condensers have, even at high frequencies (more than 50 kHz) very good capacitance and impedance values, high capacity substantially independent of frequency, low dielectric loss, and low leakage current.

Description

The invention relates to a method for producing cones capacitors, consisting of a positive rectifier elec trode with dielectric oxide layer, a negative elec trode, if necessary separating foils and usual contact conditions where an electrolyte is applied to the positive electrode brought or the release films are soaked, and as Electrolyte is used as a conductive polymer Polymerization of a solution of 3,4-ethylenedioxythiophene and Iron (III) tosylate is formed. The invention relates to fer ner capacitors produced by the process.  

Solid-state capacitors are already known, e.g. B. TCNQ capacitors (see DE-OS 32 14 355 and 36 34 987), MnO ₂ capacitors and polymer capacitors with electrochemically applied polymer (see EP 02 85 728 A1).

Such solid-state capacitors, which are simple in the following are referred to as capacitors, are characterized by gün other electrical properties. For their manufacture however, in some cases complex manufacturing processes are required.

Capacitors usually consist of a metal foil, e.g. B. an aluminum foil, which is a dielectric oxide layer and serves as a positive electrode, another Metal foil, which serves as a negative electrode and one or several separating foils, e.g. B. made of paper, especially if it is so-called winding capacitors. With such con However, the positive rectifier electrode can be used as a capacitor also be a sintered body, in particular a tantalum sintered body per with dielectric oxide layer. Such capacitors around continue to make a common contact, which in itself known manner preferably with a graphite and / or Leitsil Coating takes place.

In the case of so-called winding capacitors, which a paper film is used as a release film, this is Condenser paper is usually charred to its specific to reduce resistance. This "carbonization process" Process mentioned usually takes 10 to 30 hours and is at a temperature between 200 and 300 ° C, preferably at 300 ° C carried out.

In the unpublished EP 03 40 512 A2 the Use as solid electrolytes in electrolytic condensates Ren and the electro containing these solid electrolytes  Lyt capacitors described polythiophenes, which from Struk units of the formula

are constructed and in which R ₁ and R ₂ independently of one another represent hydrogen or a C ₁ -C ₄ alkyl group or together form an optionally substituted C ₁ -C ₄ alkylene radical or a cyclohexylene-1,2 radical. These special polythiophenes can be applied in a particularly simple manner without affecting their conductivity to the metal foils used as anodes in electrolytic capacitors.

The object of the present invention is that in the EP 03 40 512 described basic coating process so white to develop that solid-state capacitors with particular even at high frequencies (<50 kHz) very good capacitance and Impedance values can be obtained. Furthermore, this festival is said to be body capacitors due to good electrical properties, e.g. B. a high, largely frequency-independent capacity, low Dielectric losses and low leakage currents.

This object is achieved according to the invention in that the conductive polymer through several successive polymers risk cycles formed from multiple solutions becomes.

Preferred embodiments of the method according to the invention are specified in claims 2 to 15 and are in described in more detail below.  

In connection with the implementation of the invention The process uses a conductive polymer as the electrolyte det by polymerization of a solution of 3,4-ethylenedi oxythiophene and iron (III) tosylate in situ on the positive Electrode of the capacitor and possibly also in the Separating foils of the capacitor by impregnating them with the bottom lymerization solution is formed.

The polymer formed in this polymerization includes orga African units of the following structural formula:

The two components of the polymerization solution are in ge suitable solvents used, 3,4-ethylenedio xythiophene usually in acetone and alcoholic solutions solution, e.g. B. in isopropanol, and iron (III) tosylate as a solution  is used in isopropanol. The concentrations of the Ethy lendioxythiophens in solution in acetone or isopropanol are usually in the range from 30 to 60% by weight and Concentration of iron (III) tosylate in the solution in Isopro panol in the range of 10 to 30 wt .-%.

The polymerization solution is usually only shortly before Placing in the capacitor, d. H. before applying on the positive electrode or the impregnation of the separating foils or the Capacitor construction with the polymerization solution, by together Menischer mixed, since the iron (III) tosylate as Initia Tor for the polymerization of 3,4-ethylenedioxythiophene in serves the solution and therefore such a solution is not unlimited is storable.

The inventive one providing the desired benefits Step now consists of the conductive polymer, which is used as the electrolyte in the capacitor by meh Multiple successive polymerization cycles from multiple to form applied solutions. This means that after each time a polymerization solution is applied The polymerization cycle is largely completed leaves. This requires depending on the prevailing temperature Periods between 10 min and 1 h, the periods at lower temperatures usually not less than 30 min are.

This ensures that the conductive polymer Roughening greatly enlarged anode surface covers and thus makes optimal electrical contact.

This is an essential requirement for good electri properties of the solid-state capacitor.  

In addition to achieving high temperature resistance the influence of moisture is also significantly reduced. Contrary Expect the polymer to be inert to water, which is means that with water none of the conductivity is destroyed reaction takes place.

Because of the method according to the invention, it is particularly possible without problems, gentle on moisture, d. H. slower to eliminate, which reduces value changes to a minimum decorate.

According to a further advantageous embodiment, the individual polymerization cycles at different temperatures tures carried out, the polymerization temperatures of -5 ° C to + 70 ° C, preferably from -5 ° C to + 90 ° C. nen. This has the advantage that the structure is very uniform of the conductive electrolyte is reached in the capacitor, without too large cavities, especially by Ver evaporate the solvent.

The polymerization cycles are advantageously carried out in this way led that first the polymerization at temperatures in Range from -5 ° C to 20 ° C, preferably from -5 ° C to 10 ° C too Begin and that the subsequent polymeri station cycles gradually increasing to temperatures of 70 ° C to 90 ° C can be carried out.

Advantageously, at least three polymerization cycles klen carried out, the polymerization cycles expedient sometimes at -5 ° C to 20 ° C, preferably 20 ° C, 45 ° C to 55 ° C, preferably 50 ° C and 80 ° C to 90 ° C, preferably 85 ° C by be performed. The upper limit of the number of polymerisa tion cycles is around six for economic reasons Polymerization cycles.  

According to a further preferred embodiment, the he most polymerization cycle, which expediently at least can be repeated once, at a temperature of -5 ° C to 20 ° C, preferably from -5 ° C to 10 ° C, wherein it is advantageous if after applying the solution in a polymerization cycle a period of 20 to 30 minutes pass until the next polymerization solution opens brought, d. that is, a sufficient amount of time remains thus the solvent contained in the polymerization solution can evaporate.

According to a further preferred embodiment, Po polymerization cycles, which occur at temperatures below 20 ° C are carried out, following the usual Polymeri sation time from 10 min to 30 min Temperatures of 20 ° C to 60 ° C for at least 30 min leads. This requires a more complete evaporation of the in the Solution contained solvent. Here, a polymer comprises the application cycle or the watering with the bottom polymerization solution and the subsequent time of the Auspolyme rization and the at least partial evaporation of the Lö means.

If after such a polymerization cycle, which at Tempe temperatures below 20 ° C was carried out, a temper act at temperatures from 20 ° C to 60 ° C for at least 30 min and usually not more than 2 h, must be carried out before the next polymerization cycle at a temperature below 40 ° C a previous cooling development of the condenser subjected to the annealing treatment gene.  

Furthermore, it is advantageous if after completion of the polymer sation or the polymerisation cycles a final heat treatment for at least 2 hours and usually not carried out for more than 20 h at temperatures from 70 ° C to 100 ° C becomes.

Advantageously, a with the conductive polymer Electrolyte-provided capacitor after complete Auspoly merisation with a casting resin, advantageously an epoxy resin encased.

A further optimization of the impregnation or coating process is advantageously achieved in that the applied during each polymerization cycle Solution amount is dosed so low that a premature Polymerize the end faces of the capacitor body and remains. By the end faces of the capacitor body or Wrap are kept free, it is ensured that also solution into the interior of the condenser during subsequent cycles body can penetrate.

Since several polymerization cycles are carried out, the a complete filling of the condenser without any problems body or winding possible with the polymer. Through here is the same for different temperature levels timely ensured that the solvent during the poly Merization evaporates relatively slowly and for example Polymer layers already formed on the film surface don't burst again and peel off.

Due to the particular with regard to a uniform loading layering and a high degree of filling achieved optimization of the Impregnation or coating process is now preferred it is also possible to use non-carbonized release films  turn. Get that without carbonizing the roll beforehand Electrical values are much cheaper, for example than that of a carbonized winding TCNQ capacitor.

The carbonization also eliminates the associated issues strong thermal loads on the oxide layer, causing in particular results in an improved residual current behavior. With the absence of carbonization is also the case with manufacturing occurring mechanical loads are reduced.

To the good electrical who despite the lack of carbonization ten, especially tan δ and Z values, also carry the following properties of the monomeric thiophene solution:

• - low viscosity over a wide temperature range away
• - Very good wettability of electrolytic capacitor papers
• - Good controllability / optimizability of the filling level of the paper size trize by multi-cycle polymerization with appropriate Temperatures.

Due to the high polymer conductivity there is also a if necessary, increase in specific resistance practically no influence on the electrical capacitor values. Otherwise there is basically the possibility of resistivity of the paper-polymer mixture the use of papers with lower bulk density continues to increase to reduce.

Finally, there is also a frequency response, which despite the lack of carbonation is even cheaper than at  for example the comparable TCNQ capacitors with carboni sized winding or even that of wet electrolytic capacitors.

An improved residual current behavior is advantageously achieved in that the oxide layer is regenerated by a formation, preferably by a standing bath formation, before the successive polymerization cycles are carried out. Furthermore, the impregnated capacitor body or Wic kel with a gradually increasing forming voltage at ge low current load (area power density of 10 to 100 mW / cm ² ) can be reformed. Finally, the avoidance of mechanical loads on the winding during manufacture has a favorable influence on the residual current behavior.

For example, for polymer capacitors with non-carbonized Residual current with relatively little variation was possible values below 1 µA can be achieved. This is likely in the first place to the thermi that is no longer applicable when carbonization ceases to exist stress. Because that is out concluded that due to different thermal expansion nation coefficients of, for example, aluminum and aluminum nium oxide microcracks occur that only during post-forming are incompletely healed.

The invention is based on two embodiments examples explained in more detail.

I. A dry wrap of a 1 µF aluminum electrolyte condenser tors was carbonized at 300 ° C for 20 h.  

This carbonized wrap was freshly made with one before issued mixture

• a) 0.5 g of iron (III) tosylate in 2 g of isopropanol and
• b) 0.25 g of 3,4-ethylenedioxythiophene in 0.35 g of isopropanol meh subjected to more polymerization cycles. For this purpose first a few drops of the polymerization solution at 0 ° C applied to the wrap and left for 20 min. These Impregnation treatment followed by a 20-minute poly merization was repeated twice. Then could the coil warm up to 20 ° C, whereupon it at 30 min this temperature was maintained.

This was followed by another impregnation and polymerisation sation for 30 min at 0 ° C, then the wrap could Warm to 20 ° C, whereupon he was at this temperature for 60 min was held. A postpolymerization then took place tion at 50 ° C for 60 min.

Finally, heat treatment was carried out for 17 hours at 85 ° C, after which the capacitor is coated with epoxy resin has been.

The polymer capacitor produced in this way showed the following electrical values, which a typi , produced using a wet electrolyte Capacitor are compared:  

Table 1

II. In another, made according to the method described polymer capacitor, a non-carbonized ter type EKF 1 uF / 50 V with dimensions 4 × 7 mm ^{2 was} used.

The polymer capacitors produced in this way showed the following electrical values, the polymer capacitors with carbonized winding, a TCNQ capacitor with carboni opposite winding and wet electrolytic capacitors represents are.

Table 2

It is Z. B. to recognize that the polymer capacitor with not carbonized wrap has significantly more favorable values than the TCNQ capacitor with carbonized winding.

In addition, the polymer con according to the invention is distinguished also by good temperature and frequency behavior capacity.

The frequency response is cheaper than, for example, that comparable TCNQ capacitors with carbonized winding or even that of wet electrolytic capacitors.

Claims (16)

1. A process for the production of capacitors, consisting of a positive rectifier electrode with dielectric oxide layer, a negative electrode, optionally separating foils and conventional contacts, in which an electrolyte is applied to the positive electrode or the separating foils are soaked with it, and as an electrolyte Is used conductive polymer, which is formed by polymerizing a solution of 3,4-ethylenedioxythiophene and iron (III) tosylate, characterized in that the conductive polymer is formed by several successive polymerization cycles from multiple applied solutions. 2. The method according to claim 1, characterized, that the individual polymerization cycles at under different temperatures are carried out. 3. The method according to claim 2, characterized, that the polymerization cycles starting at temperatu ren from -5 ° C to 20 ° C, preferably from -5 ° C to 10 ° C and gradually increasing to temperatures of 70 ° C to 90 ° C can be carried out. 4. The method according to any one of the preceding claims, characterized, that carried out at least three polymerization cycles will. 5. The method according to claim 4, characterized, that the polymerization cycles at -5 ° C to 20 ° C, before preferably 20 ° C, 45 ° C to 55 ° C, preferably 50 ° C and 80 ° C to 90 ° C, preferably 85 ° C are carried out. 6. The method according to any one of claims 3 to 5, characterized, that the first polymerization cycle at a tempera Repeat at least once from -5 ° C to 20 ° C becomes. 7. The method according to any one of the preceding claims, characterized, that according to the individual, at temperatures below 20 ° C carried out polymerization cycles a tempera Turbo treatment at temperatures from 20 ° C to 60 ° C for is carried out for at least 30 minutes.   8. The method according to any one of the preceding claims, characterized, that after completion of the polymerization or Polymerisa a final heat treatment during at least 2 hours at temperatures from 70 ° to 100 ° C is carried out. 9. The method according to any one of the preceding claims, characterized, that the capacitor after the introduction of the electroly in the form of the conductive polymer with epoxy resin is enveloped. 10. The method according to any one of the preceding claims, characterized, that a solution is used, which is isopropanol and / or acetone as a solvent. 11. The method according to claim 10, characterized, that a 20 to 60 wt .-% solution is used. 12. The method according to any one of the preceding claims, characterized, that during a particular polymerization cycle the amount of solution applied is dosed so low, that premature polymerization of the end faces of the capacitor body is omitted. 13. The method according to any one of the preceding claims, characterized, that non-carbonized release films are used.   14. The method according to any one of the preceding claims, characterized, that the oxide layer on each other before performing the following polymerization cycles through formation, preferably regenerated by a standing pool formation becomes. 15. The method according to any one of the preceding claims, characterized, that the impregnated capacitor body or winding with a gradually increasing forming tension at gerin ger current load is reformed. 16. Capacitor made by the method of a of the preceding claims.