JP2008519440A - Method and system for forming high voltage anodic oxide on a valve metal anode - Google Patents

Abstract

  A method and system for forming a high voltage anodic oxide on a valve metal anode. This method generally includes a step of immersing the valve metal anode in an electrolyte forming bath containing the forming electrolyte, a step of performing the anodizing step, and a temperature of the forming electrolyte during the anodizing step of 40 ° C. or lower. Maintaining or adjusting the temperature accurately. Anodization is first performed at a constant current until the target potential is reached, and second, at a constant target potential until the current drops below a predetermined stop current level. The system generally includes a tank configured to receive one or more anodes in an electrolyte forming bath containing a forming electrolyte, and a subsystem for cooling and maintaining the forming electrolyte at a desired process temperature. including. The system may further include an electronic controller for monitoring and adjusting system or method parameters.

Description

  The present invention relates to a method and system for forming a high voltage anodized valve metal anode for use in wet electrolytic capacitors. This type of anode is particularly suitable for use in high voltage capacitors for use in implantable medical devices (IMDs).

  The term “valve metal” is a term representative of a group of metals including aluminum, tantalum, niobium, titanium, zirconium, and the like. All of these metals, when subjected to anodic polarization in a conductive solution, such as a forming electrolyte, form a sticky, electrically insulating metal oxide thin film. The wet electrolyte capacitor generally includes an anode, a cathode, a barrier layer that separates the anode and the cathode, that is, a separator layer, and an electrolyte. In a tubular electrolyte capacitor, the anode is typically made of a wound anodized aluminum foil, with subsequent rolls separated by at least one separator layer. Flat electrolyte capacitors can include stacked sheets of anodized aluminum or tantalum sintered structures, which are separated from the cathode by at least one separator layer, as described in more detail below. Is done. Such electrolyte capacitors have a wide range of industrial applications, including implantable medical devices (IMDs) such as external and implantable defibrillators.

  Various IMDs are well known in the art, as described in commonly assigned US Pat. No. 6,006,133. Of particular interest is the relatively high energy of the patient's heart when potentially fatal tachycardia (eg, ventricular fibrillation, ventricular tachycardia, atrial tachycardia, atrial fibrillation) is detected. An implantable cardioverter-defibrillator (ICD) that performs cardioversion and / or defibrillation therapy. Before performing high-voltage therapy, one depending on the type of treatment desired (ventricular defibrillation, atrial defibrillation, etc.) and the type of device (eg, external or internal device) Or quickly charge a higher voltage capacitor to a higher voltage. In practice, typically a relatively low voltage battery is connected to a step-up (eg, horizontal deflection output) transformer to discharge the capacitor across the target myocardium. Treatments performed include customized waveforms (biphasic polarity, steep or sloped leading edge, exponential decay, etc.) and timed appropriately for the patient's heartbeat that appears after this.

Current ICDs also typically have single-chamber or two-chamber pacing capabilities to treat certain chronic or recurrent atrial and / or ventricular bradycardia and tachycardia, It was called pacemaker / defibrillator / defibrillator (PCD). Early implantable automatic defibrillators (AIDs) did not have cardioversion or pacing capabilities. For the purposes of the present invention, an ICD is an external device known as an automatic external defibrillator (AED), as well as all such IMDs having at least high voltage cardioversion and / or defibrillation performance. Is understood to include.
US Pat. No. 6,006,133

  Energy, volume, thickness, and mass are important features in designing an ICD implantable pulse generator (IPG) connected to an ICD lead. As devices become more common, more efficient, lower in price, and certain AEDs have recently become unnecessary for physician prescribing, such devices become smaller and more portable. Both ICDs and AEDs have traditionally used relatively bulky and expensive batteries and high voltage capacitor units to provide the energy needed to perform the treatment provided by these devices. Currently, ICDs typically have a volume of about 40 cc to about 60 cc, a thickness of about 13 mm to about 16 mm, and a mass of about 100 g.

Reducing the volume, thickness, and mass of such capacitors and ICDs without reducing the deliverable energy to make the patient comfortable and to minimize complications due to the folds of tissue surrounding the ICD It is advantageous. In addition, miniaturizing the capacitor can add volume to the battery, thereby extending the life of the ICE or adding new components, thereby adding functionality and additional features to the ICD. Furthermore, it would be desirable to be able to provide such an ICD at a low price while maintaining the highest level of performance. At the same time, the reliability of the high voltage capacitor is not impaired. Electrolytic capacitors based on aluminum or tantalum have typically been used as high voltage ICD capacitors. The aluminum electrolyte capacitor incorporated into the ICD was filed on June 30, 2000 in the name of Yang et al. It is disclosed in co-assigned US patent application Ser. No. 09 / 607,830, entitled “Implantable Medical Device”.
US patent application Ser. No. 09 / 607,830

  The performance of an electrolyte capacitor depends on several factors such as the effective surface area of the anode and cathode that can be contacted by the electrolyte, the dielectric constant of the oxide formed on the metal surface, the thickness of the oxide layer on the metal surface, the conductivity of the electrolyte, etc. It depends on these factors. In all electrolyte capacitors, the thickness of the anodic oxide layer is approximately proportional to the potential applied to the anode during formation of the anode, i.e., when the anode is immersed in the forming electrolyte. For aluminum, the oxide grows about 1.2 nm per volt, and for tantalum, this “rate” is somewhat higher, about 1.7 nm per volt.

Niobium and tantalum anodes, when used in electrolyte capacitors, are typically formed in the form of compressed powder pellets or “slags”. The density of the anode slag is typically much less than the density of the metal itself, i.e. up to 2/3 of the volume of a given slag is open, i.e. a small pore space. The final density of the anode slag is largely determined upon compression, that is, when a known amount of powder is compressed to a known volume. In order to properly form the anode slug, it is important to distribute the pores very evenly across the anode slug. This is because many “remote” cavities or gaps in the anode karst internal structure need to be evenly wetted with the forming electrolyte. This is particularly important for relatively large anodes with a volume on the order of 1 cm ³ or more.

  Furthermore, it is important that the electrolyte flows very easily through the structure. This is because a large amount of power is dissipated as heat during the forming process. During the formation of the oxide layer on the surface and gap of the valve metal anode, a local potential difference of several hundred volts and a local current density of several tens of mA are encountered (ie, 20-30 W are dissipated as heat). If not adjusted in any way, the dissipated heat adversely affects the quality and performance of the anode, as discussed in more detail below.

As is well known to those skilled in the art, various methods are used to evenly distribute the small holes throughout the anode. Conventional methods for forming oxide layers are described in the prior art, for example, US Pat. No. 6,231,993, US Pat. No. 5,837,121, US Pat. No. 6,267,861, and Described in the patents and literature mentioned above. An example of an improved method for forming a high performance valve metal anode that can be incorporated into an IMD was filed on Oct. 23, 2003, entitled “High Performance Valve Metal Anode with Complex Internal and Surface Features. And its processing method ”are disclosed in commonly assigned US patent application Ser. No. 10 / 692,649. It is assumed that the contents disclosed in this patent application are included in this specification by touching this patent application. Typically, a power source capable of delivering a constant current and / or potential is connected to an anode slug immersed in the electrolyte. The current through the anode-electrolyte system is then constant and the potential is raised to the desired final potential.
US Pat. No. 6,231,993 US Pat. No. 5,837,121 US Pat. No. 6,267,861 US patent application Ser. No. 10 / 692,649

  Regardless of the method of processing the valve metal powder, the valve metal powder structure is typically compressed and sintered by the controlled application of forming potential and current with the anode immersed in the fluid-forming electrolyte. Anodizing (for example, tantalum, niobium, etc.) is performed. A typical forming electrolyte includes ethylene glycol or polyethylene glycol, deionized water, and H3PO4, and has a conductivity of 50 μS / cm (micro Siemens per cm) to about 20000 μS / cm at 40 ° C.

Conventionally, an anode-polarized valve metal is formed in accordance with the target formation potential while a constant current is passed through the anode-electrolyte system. Typically, a stainless steel cathode was used with an electrolyte containing glycol. The magnitude of the current is determined by the electrolyte, the type of valve metal powder, and the size of the valve metal structure. Most of the current flowing through the anode-electrolyte system is used to electrolyze water in the anodization process described below.
[Anode method]
10OH ⁻ + 2Ta → Ta ₂ O ₅ + 5H ₂ O + 10e ⁻
[Cathode method]
10H ⁺ + 10e ⁻ → 5H ₂

Therefore, the current setting has a direct effect on the speed of the anodization reaction, and when using Faraday's law, the formation current is very low (for sintered tantalum samples, the low current is 0.1 μA / Cm ^{2 to} about 1 μA / cm ² ) and a long formation time of well over one week for the anode size and target formation potential associated with the ICD capacitor You can easily show what to do. Adjusting these parameters according to the prior art is within the ordinary knowledge of the person skilled in the art. A predetermined thickness that allows the anode to hold the charge at the desired operating potential for an appropriate duration, and that the dielectric layer (tantalum pentoxide covering the tantalum anode) does not leak excessive amounts of charge outside. And when the structure is reached, the anode is said to be fully formed. The amount of charge that leaks out per unit time is called the leakage current of the capacitor. In any case, a typical formation method takes 1 to 250 hours depending on factors such as the size and porosity of the anode structure and the viscosity, temperature, and conductivity of the electrolyte.

  US Pat. No. 5,837,121 listed above uses a specific electrolyte and usually applies a constant potential and current as described in US Pat. No. 6,231,993 above. It is disclosed to apply the potential and current in a manner different from the manner in which it is performed. The electrolyte of US Pat. No. 5,837,121 includes a glycerin solution of dibasic potassium phosphate. The electrolyte has been heated to 180 ° C. for 1 to 2 hours or 150 to overnight. An electrolyte that has been subjected to such heat treatment is reported to exhibit a completely different behavior when used as an anodizing electrolyte at 150 ° C. or higher compared to an electrolyte that has not been heat treated. The heat treated electrolyte solution is believed to provide an anodic film for tantalum and other valve metals. Such thin films are not limited in thickness according to the anodizing voltage, but instead continue to grow thicker as long as an anodizing potential is applied.

  U.S. Pat. No. 5,837,121 has a relatively uniform thickness within and on the surface of a sintered tantalum powder capacitor anode when the potential applied to the anode body is applied as pulsed direct current (DC). Claims that it can produce a thin film. The positive bias pulse continues to be applied for about 0.3 seconds or less, with a no-bias or open circuit period between pulses of at least 0.3 seconds. It is further taught that alternating current (AC), half-wave AC, sawtooth waveform, etc. can be used instead of pulsed DC to obtain uniform thin films within these electrolytes. However, no further details are given. Clearly, in US Pat. No. 5,837,121, the purpose of applying a pulsed potential is to support oxide growth whose thickness is not limited by the forming potential.

In the above-mentioned US Pat. No. 6,231,993, there is a problem with the conventional valve metal anodizing method because the electrolyte is heated inside the gaps or small holes of the porous tantalum pellets during the anodizing method. It has been reported. The electrolyte is heated by dissipating power in the form of heat within the anode structure. Power dissipation is anisotropic, that is, when certain local areas within the anode are very hot, other areas are relatively cold. In the high temperature region of the karst-like structure that can be likened to a steam vessel assembly, the internal pressure increases causing the electrolyte to decompose and / or crack the sintered structure. As a result, instability is introduced into the system and the performance of the capacitor is adversely affected. Such instabilities are of course unacceptable. Therefore, in order to anodize large sintered anodes with a volume of 1 cm ³ and higher, thermal management of the anode system during anodization becomes important.

  U.S. Pat. No. 6,231,993 discloses that the heated electrolyte in the anodized structure is periodically diffused with new electrolyte from the anodized electrolyte bath during the period of quenching of the applied formation potential. It is taught to replace. In other words, the formation potential is periodically reduced to zero for a time long enough to cool and diffuse the electrolyte inside the pellet. Thus, the hot condensed electrolyte, which becomes a solid residue when heated over time, can be replaced with new electrolyte from the anodizing bath during the period in which the forming potential is extinguished.

  Further, according to the description of US Pat. No. 6,231,993, the current is stepped down in relation to the increase in formation potential. In one of several examples described in US Pat. No. 6,231,993, first, the current I1 is set to about 80 mA per 8 g of anode. The current I1 is maintained until the formation potential V1 = 75V is reached. Following this step, the formation potential is extinguished for 3 hours. Thereby, an anode pellet can be cooled and electrolyte can be replenished. Next, the potential is increased stepwise. The magnitude of the potential increase decreases as the potential increases. At the same time, the current that can flow through the system decreases. In a potential regime slightly lower than the target formation potential (eg about 231 V), the current setting in the example cited above is just 31 mA, or about 1/3 of the initial current setting.

  In another example, the remaining interval is on the order of 1 hour and the forming potential step is applied over 1 to 3 hours. This method is obviously very time consuming, as can be easily estimated using Faraday's law. Furthermore, applying the method described in US Pat. No. 6,231,993 results in a long anodization time during which a low current is used and a high voltage, specifically a target formation potential. A slightly lower voltage regime is used.

  L. L. According to the Odinez model (see pages 1591 to 1594 of the Soviet Electrochemical Journal 23 (12), 1987), these conditions are favorable for the occurrence of field crystallization and during in situ precipitation. Crystalline tantalum pentoxide grows at the metal-oxide interface, preferably under an amorphous oxide grown under high current forming conditions. In the long run, the anode is destroyed by the growth of crystalline oxide species under the previously grown amorphous layer. In the short term, the leakage current is undesirably high due to crystal growth. Therefore, the conditions for forming a high current at a low current are avoided or maintained for as short a time as possible.

  US Pat. No. 6,231,993 does not mention another important component of anodization, namely electrolyte agitation. Advantageously, a substantially isotropic temperature distribution can be maintained across the anode by stirring during anodization. Typically, a stirring impeller (for example, a rotating magnet) is disposed in the solution, and the electrolyte is stirred by rotation.

US Pat. No. 6,235,181 to Kynard et al. Emphasizes the need to stir the electrolyte during the forming process, and as a variation on using a stirrer impeller, ultrasonically stir the electrolyte during the anodizing process. Is taught to do. However, the use of ultrasonic agitation in US Pat. No. 6,235,181 clearly relates to the above-described anodizing method without the thickness limitation of the sintered Ta anode, where a very special electrolyte (heat treated) is used. The second potassium phosphate dissociated in glycerol is taken up. This electrolyte should be used at a temperature of 150 ° C. or higher, and it is difficult to avoid a temperature regime in which the temperature varies locally. Ultrasonic agitation is added to eliminate or “dramatically reduce” temperature fluctuations in the electrolyte bulk, especially at these relatively high electrolyte temperatures.
US Pat. No. 6,235,181

  Briefly, prior art anodization methods for relatively large high voltage wet electrolyte valve metal anodes require significant precious production time and low yield. This is either because the anode becomes unusable due to sticking of the electrolyte decomposition products, or due to in situ deposition, the leakage current becomes unacceptably high.

  Accordingly, there is a need to define a new and improved formation method for high voltage electrolyte valve metal anodes. Such a method must provide a fully formed anode with a high yield and must be more economical than the methods reported in the patent literature. That is, it must be short and / or be able to use a relatively high current setting throughout the entire formation cycle.

  Many IMDs typically include a battery and at least one capacitor. The capacitor is operatively coupled to a microelectronic device disposed within the hermetic housing. The housing is adapted to receive the proximal end of one or more medical electrical leads for delivering electricity in therapy. The components placed in the housing occupy about 1/3 of the IMD volume. For many reasons, the volume of at least one of these parts can be reduced and the capacity or volume of one or both of the two parts can be increased, or the overall size or volume of the IMD can be reduced. It is desirable to do. Accordingly, there is a need to provide a method and apparatus for forming a high voltage valve metal anode that is small in volume and thus provides a small high energy capacitor for use in an ICD.

  Traditionally, in an attempt to optimize the performance of a capacitor, during the processing of the anode (eg, processing to form a surface oxide on the anode) and subsequent operation as an electrochemical cell, the free flow of the liquid electrolyte is reduced. Have been used. One reason is related to the electrolyte used during anodization (which is often referred to as the “forming electrolyte”) being overheated in the gaps of the anode. During formation, a power source capable of delivering a constant current of about 100 mA per anode and a constant potential of several hundred volts is connected to the anode slug immersed in the electrolyte. Electrical energy on the order of 20-30W per anode is dissipated as heat and encounters local differences in applied potential. This overheating adversely affects the formation of oxides and accumulates electrolyte residue (polymeric adhesive) in the small holes and gaps. During operation of an electrochemical cell, a continuous free circulation of the electrolyte, typically referred to as the “working electrolyte”, is required in order to quickly access the charge, even in fine cracks. That is, ions in the electrolyte must be able to migrate rapidly in order to offset the charge on the metal electrode. Such charge transfer occurs during the charge / discharge cycle of the capacitor.

  Such adhesive deposits of electrolyte residue undesirably block the void space to be occupied by either the forming electrolyte or the working electrolyte, preferably during anodization or during the operation of an IMD electrochemical cell. It will end up. The presence of such residues adversely affects the crystal structure of the oxide during formation, adversely affects ion migration within the forming electrolyte during formation, or adversely affects the working electrolyte during operation. In addition, such residue reduces energy density by reducing capacitance, impairs the performance of the finished electrochemical cell, and increases the internal resistance of the capacitor (also known as equivalent series resistance or “ESR”). This prevents rapid discharge and recharging of the capacitor.

  The residue further reduces the efficiency of the condenser, measured as the ratio of the condenser outflow energy to the inflow energy (Eout / Ein). For comparison, the capacitor can have an efficiency of about 85%. In the field of IMD, increasing energy density provides an effective improvement. Although not bound or limited by theoretical or experimental observations, the inventor has determined that the energy density is at least 5% in one or more of the various embodiments of the method and system of the present invention. I found that I could rise.

  Thus, the present invention discloses, describes, illustrates and claims, by way of example and not limitation, a method and apparatus for forming a high voltage valve metal anode. This reduces or eliminates the formation of electrolyte residue adhesions, improves oxide structure, reduces ESR, increases capacitance, increases energy density, and shortens formation time. Or more. One or more of these advantages may be realized by one or more of various embodiments of the method and apparatus of the present invention.

  The present invention provides various embodiments of methods and systems for forming a high-voltage, anodic oxide on a valve metal anode. Various embodiments of the method according to the teachings of the present invention generally provide a method of forming high voltage anodic oxide on a valve metal anode. The method includes the steps of immersing the valve metal anode in an electrolyte forming bath containing a forming electrolyte, performing the anodizing process, and in the forming bath during the anodizing process. Maintaining the temperature of the forming electrolyte at a relatively low temperature (40 ° C. or lower). In one form of the invention, the temperature of the forming electrolyte is maintained with an accuracy of about ± 2 ° C. The accuracy in maintaining the temperature of the forming electrolyte is generally achieved by cooling the forming electrolyte under control. In some embodiments of the present invention, the method of anodizing comprises applying a potential at a constant current until the target potential is reached, and then the target potential until the current drops below a predetermined stop current level. Applying a potential of In a variation of the embodiment of the method of the present invention, the anode may be removed from the forming electrolyte, subjected to a heat treatment, and the anodization step repeated.

  In one embodiment of the present method for forming an oxide layer, a method is provided for forming a high voltage anodic oxide on a valve metal anode. In this method, the step of immersing the valve metal anode in an electrolyte forming bath containing the forming electrolyte and the anodizing step are performed at a constant current until the target potential is reached, and then at the target potential, the current is stopped for a predetermined amount. Performing until the current level drops below, circulating the forming electrolyte flow from the forming bath through a heat exchanger to provide a cold flow of forming electrolyte, and during or around the forming bath during anodization Accurately maintaining the forming electrolyte in the forming bath at a relatively low temperature (eg, 40 ° C. or below) by the relatively low temperature forming electrolyte flow.

  In another embodiment of the method of the present invention, a method for forming a high voltage anodic oxide on a valve metal anode is provided. In this method, providing an electrolyte forming tank with an electrolyte forming bath containing a forming electrolyte formed to receive one or more anodes, and an electrolyte circulation sub for circulating and cooling the forming electrolyte. Providing the system, immersing one or more anodes in the forming electrolyte, circulating the forming electrolyte from the forming bath through the circulation subsystem, and providing a cold flow of forming electrolyte; Or applying a predetermined potential to more anodes and increasing the potential to a target voltage until a target potential is reached with a constant current applied; and one or more anodes having a predetermined current A process of continuing to apply the target potential until the current drops below the stop current level of the current, and forming voltage in the forming tank while the potential is being applied. As the temperature of the quality is accurately maintained at 40 ° C. or lower temperatures, and a step of adjusting the flow rate and temperature of the electrolyte.

  In one embodiment of the system according to the present invention, an electrolyte bath system is provided. The electrolyte bath system includes a tank with an electrolyte forming bath that includes a forming electrolyte that is configured to receive one or more anodes. The tank is formed with a fluid inlet and a fluid outlet. An electrolyte circulation subsystem is provided that is connected in flow communication with the tank. The subsystem is configured to accept the electrolyte flow from the outlet to reduce the temperature of the electrolyte flow and to return the electrolyte flow to the fluid inlet. In a variation of this embodiment, instead of the electrolyte circulation subsystem, the tank walls are brought into direct contact with the cooling fluid or medium for heat transfer.

  In another embodiment of the system according to the present invention, an electrolyte bath system is provided. The electrolyte bath system is a tank having a lower level and an upper level in flow communication with the lower level, the lower level having an inlet configured to receive the flow of electrolyte into the tank, and The level has an outlet configured to drain the electrolyte flow from the tank, and the upper level is formed with a plurality of anode forming slots that are sized to receive at least one anode. Each of the slots has an opening through which the electrolyte flows from the lower level into the upper level and an electrolyte circulation subsystem coupled to the inlet and outlet.

  In these and other embodiments of the system according to the invention, the electrolyte circulation subsystem comprises a heat exchanger coupled to the cooling unit and at least one for circulating electrolyte between the tank and the electrolyte circulation subsystem. A pump. The circulation subsystem may further comprise at least one pump or blower for circulating cooling fluid through the cooling unit. In some embodiments of the system according to the invention, the tank may be a closed housing with a lid, so that the system forces the forming electrolyte into the smallest crack of the karst sintering process. Further, a vacuum unit may be provided.

  In yet another embodiment of the system according to the present invention, in an electrolyte bath system, a tank with an electrolyte forming bath containing a forming electrolyte, the tank being configured to receive one or more anodes. The tank has inner and outer walls spaced to form a plenum through which cooling fluid can circulate, an inlet for receiving cooling fluid into the plenum, and an outlet for discharging the cooling fluid from the plenum. A bath system is provided that includes a tank having a cooling fluid circulation subsystem coupled in flow communication with an inlet and an outlet. In order to maintain the temperature of the forming electrolyte, or to adjust the electrolyte flow rate and temperature in various embodiments of the present invention, the system further includes: electrolyte circulation rate, heat transfer rate, and cooling fluid circulation rate. It is equipped with an electronic control unit that is equipped and configured to adjust one or more.

  The present invention is particularly useful for forming high voltage, high capacitance anodes. This is because the dissipation of thermal energy can be managed during the formation process, and the yield of a fully formed anode is improved with improved energy density and low leakage current at the operating voltage. These and other advantages and features of the present invention will be considered in the following detailed description of a preferred embodiment of the invention in conjunction with the accompanying drawings in which like reference numerals refer to like parts throughout the drawings. Will be better understood.

  The present invention provides a novel method and system for forming and manufacturing a compact AVM anode with high voltage, high capacitance, and high energy density. As described in further detail herein, the various embodiments and forms of the present invention provide distinct advantages over the prior art. Although only a few valve metals known to be used in connection with IMD are described herein, the present invention is not limited thereto. For example, any valve metal may be used when practicing the present invention.

  By way of example and not limitation, metals such as tantalum, niobium, aluminum, zinc, magnesium, zirconium, titanium, hafnium, palladium, iridium, ruthenium, molybdenum, and combinations and / or alloys thereof may be used. The metal used can take the form of an etched sheet or a pellet compressed from a powder material. In one aspect, each of the metals can accurately and predictably control the thickness of the oxide during formation and has a dense and tightly adherent electrically insulating (eg, high dielectric strength and high dielectric constant). ) Form an oxide. Finally, although the present invention will be described primarily with respect to a liquid electrolyte, according to the present invention, the final capacitor component may use an electrolyte mixed with a solid and / or an entirely solid electrolyte.

  1 to 4 are block diagrams showing the steps of certain features of an embodiment according to the present invention. Overall, the example methods shown in these figures can be implemented with an electrolyte bath system according to the present invention. Referring now to FIG. 1, in step 102, the anode is immersed in an electrolyte forming bath and then anodized in step 104, where the temperature of the forming electrolyte is relatively low (eg, about 40 ° C. or Below that, a method 100 is shown.

  Referring to FIG. 2, a method 200 is shown in which the anode is immersed in an electrolyte formation bath at step 202 and then anodized at step 204 with a constant current until a target potential is reached. After reaching the target potential, anodization is continued until the current drops below a predetermined stop current threshold. During anodization, step 206 maintains the temperature of the forming electrolyte at a relatively low temperature (eg, about 40 ° C. or lower).

  Referring to FIG. 3, a method 300 is shown in which an anode is immersed in an electrolyte forming bath at step 302 and then anodized at step 304 with a constant current until a target potential is reached. After reaching the target potential, anodization is continued until the current drops below a predetermined stop current threshold. At step 306, the forming electrolyte is circulated between the forming bath through a heat exchanger to provide a relatively low temperature electrolyte around the anode unit. Thus, during anodization, at step 308, the temperature of the forming electrolyte is maintained at a relatively low temperature (eg, about 40 ° C. or lower) in conjunction with actively cooling the circulating electrolyte.

  Referring to FIG. 4, a method 400 for providing an electrolyte formation tank at step 402 is shown. The tank contains a predetermined volume of forming electrolyte. In step 406, one or more anodes are immersed in an electrolyte forming bath. In step 408, the forming electrolyte is circulated from the forming bath (tank) through the fluid circulation subsystem, thereby cooling the forming electrolyte. In step 410, an electrical potential is applied to one or more anodes to grow an oxide on the metal surface. During these steps, the flow and temperature of the forming electrolyte are controlled, and in step 412 the temperature is controlled to a relatively low temperature (eg, 40 ° C. or lower).

  An example of an electrolyte bath system within the scope of the present invention is shown schematically in FIG. The system 10 includes an electrolyte formation tank 20 and an electrolyte circulation subsystem 30 that is rheologically coupled to the tank 20. The tank 20 may be provided with a lid or cover 21 as shown in FIG. 5, or may not be provided with a lid or cover 21 as shown in FIG. The tank 20 can be provided with a fluid inlet 22 and a fluid outlet 24 with or without a lid. The electrolyte flows from the heat exchanger through the inlet 22 into the forming tank 20 and exits the forming tank 20 through the outlet 24. Tank 20 is further configured to receive one or more anodes and includes an electrolyte forming bath that includes the forming electrolyte discussed above and generally known to those skilled in the art. The system further includes a pump 36 for circulating electrolyte between the tank 20 and the heat exchanger 32.

  The tank 20, heat exchanger 32, and pump 36 are connected in sections made of pipes or hoses 38. In FIG. 5, the pump 36 is shown downstream from the tank 20 and between the tank 20 and the heat exchanger 32. However, the position of the pump 36 is a matter of design choice. The pump 36 may be disposed between the heat exchanger 32 and the tank 20, for example, downstream of the heat exchanger 32. In addition, one or more pumps may be used. Furthermore, when cooling is performed by stirring with an impeller and bringing the outer wall of the bath into contact with the cooling liquid, the inlet and the outlet need not be used. Further, a plurality of inlets 22 and outlets 24 may be provided in the tank. Although a single section of pipe 38 is shown, each inlet 22 and outlet 24 is connected to one section of pipe 38 connected to either a plurality of pumps 36 or a common conduit supplying a single pump 36. A plurality of sections of the pipe 38 may be provided to be connected. Similarly, the section of pipe 38 between pump 36 and heat exchanger 32 may be a single pipe section, or one branching into sections of multiple pipes 38 passing through heat exchanger 32. It may be supplied to the conduit. If necessary, heat exchange can be performed more rapidly with this configuration.

  The heat exchanger 32 is connected to the cooling unit 34. The cooling fluid flows through the cooling unit 34 and transfers heat from the forming electrolyte flowing through the heat exchanger 32 to the cooling fluid flowing through the cooling unit 34. The cooling fluid source may be any of a variety of fluids known to those skilled in the art to be suitable for this purpose. For example, the cooling fluid may be a heat transfer gas or liquid, such as air, water, liquid coolant, and the like. The cooling unit 34 is connected to a cooling fluid source (not shown in FIG. 5) via a section of a pipe 38 and a pump (not shown in FIG. 5). The cooling fluid source may be a dedicated fluid source or part of a large facility cooling system such as an industrial water system, an industrial liquid or gas cooling system, or a building air cooling system or air conditioning system. There may be.

  In operation, the flow of forming electrolyte exiting outlet 24 (indicated by directional arrow 41a) is pumped by pump 36 to heat exchanger 32 where it is cooled and then returned to inlet 22 of tank 20. When the forming electrolyte stream is introduced into the tank 20, it mixes with the forming electrolyte in the bath. The electrolyte flow circulating in the system as a whole must be sufficient to keep the temperature distribution in the formation bath constant and to avoid temperature fluctuations. However, the temperature may be more evenly distributed by stirring during the forming cycle by means well known to those skilled in the art, such as a stirring impeller or ultrasonic stirring. In order to transfer heat to ambient air in the external process environment, heat dissipation may be further assisted by providing the tank 20 with a plurality of fins and fans.

  In embodiments of the system 10 where the tank 20 includes a lid 21, the system 10 may further include a vacuum unit. In such an embodiment, the tank 20 and the lid 21 are formed of a material having sufficient strength, and are formed so as to withstand the pressure difference generated in the tank 20 due to negative pressure. Furthermore, for this purpose, the lid 21 must be able to form a vacuum tight seal when closed. When the system 10 is provided with a vacuum unit, the lid 21 and / or tank 20 is formed to form a vacuum seal when the lid 21 is closed and a vacuum is generated. The generated vacuum must be sufficient to generate a pressure differential that can force the forming electrolyte into the pores and gaps of the anode immersed in the forming electrolyte. This is done by generating a vacuum in the tank. In general, a pressure of about 20 hPa has been found suitable for this purpose.

  The embodiment shown in FIG. 6 provides one non-limiting example. The tank of this embodiment has a lower level with an inlet 22 formed to receive electrolyte flow into the tank 20. The tank further has an upper level in flow communication with the lower level. The upper level has an outlet 24 through which electrolyte flow is discharged from the tank 20 to the pump 36 or heat exchanger 32 as described above with respect to FIG. The upper level is further formed with a plurality of anode forming slots 26 into which the anode can be immersed. These slots 26 are sized to receive at least one anode.

  Each slot 26 has an opening through which electrolyte rising from the lower level passes and flows into the upper level. Electrolyte stream 41 enters the lower level through inlet 22 located in the lower portion of tank 20. The lower level and the upper level are in flow communication through the opening of the slot 26. The electrolyte rising from the lower level flows through the opening. The tank 20 of FIG. 6 may include two or more slots 26. In some methods, the tank may have one or more slots, several tens of slots, and up to 100 or more slots. The number of slots is a method engineering choice and is in fact limited by the space in which the system and its components are placed or by other considerations of the method.

  In order to maintain the temperature during the process, or to adjust the temperature and adjust the flow rate of the electrolyte, the system 10 may include an electronic controller in various embodiments thereof. The controller is configured to adjust the electrolyte circulation rate, the cooling fluid circulation rate, the heat transfer rate, or a combination thereof, and may include one or more temperature sensors. These sensors are arranged in the formation bath of the tank 20, in the heat exchanger 32, upstream and downstream of the heat exchanger 32, upstream and / or downstream of the cooling unit 34, especially at other locations. Also good. The sensor provides a temperature reading output to the controller. The control device processes data for preprogrammed control parameters.

  The controller then signals a signal to one or more subsystems, such as pump 36, or to system components to increase or decrease the flow rate of electrolyte stream 41 or cooling fluid stream 43. send. Various types of controllers known to those skilled in the art to be suitable for integrally controlling and changing temperature and flow, or for use with a heat exchanger subsystem, may be used to control system 10. Method parameters or operating parameters can be changed, monitored and / or adjusted.

  The method of forming the high voltage anodic oxide on the valve metal can be implemented in the system embodiments of the invention described hereinabove or in systems of different configurations. The method will be understood with reference to FIGS. 1-4 and embodiments of the invention derived therefrom and the following description.

  The heat generated during anodization in the electrolyte forming bath adversely affects the quality of the anodic oxide adhered to the valve metal anode. The problems of the conventional anodizing method are described above in the background art. Prior art anodization has typically been performed at temperatures between 40 ° C and 80 ° C. Recently, in co-assigned US patent application Ser. No. 10 / 058,437, one of the applicants anodized at a temperature of 40 ° C. while applying potential in the form of pulses for thermal management. Went.

  Applicants have found that the method of the present invention can improve anodic oxide adhesion. More specifically, applicants can control the heat generated during anodization by controlling the heat transferred from the forming electrolyte in the forming bath by the method of the present invention, so that the oxide It has been found that formation is improved. This can be done by circulating a flow of electrolyte from the forming bath to be cooled in the electrolyte circulation subsystem 30 or heat exchanger 32. Further, this may be done by circulating cooling fluid from the cooling fluid circulation subsystem through the plenum of tank 20 or by contacting the outer wall of tank 20 with a cooling fluid or cold environment. Good. The tank has an inner wall and an outer wall, and these walls form a plenum. In the latter case, cooling can be enhanced when the tank 20 is provided with a plurality of fins or fans for dissipating heat into the environment. This environment may simply be a chamber or space in which the tank 20 is housed, or a chamber or space in which cooling fluid is circulated between the tank 20 and the outer wall of another vessel in which another tank or tank 20 is located. It may be.

  By performing cooling under control in embodiments of the method and system of the present invention, Applicants can accurately maintain the temperature of the forming electrolyte at or below 40 ° C. with an accuracy of about ± 2 ° C. In addition, Applicants have found that providing temperature control improves the properties of the anodic oxide. Applicants have achieved such improved properties for anodic oxides adhered at temperatures of 40 ° C. or lower, 30 ° C. or lower, 20 ° C. or lower, and 10 ° C. or lower. Applicants believe that the method according to various embodiments of the present invention can be performed at temperatures of about 0 ° C. and can be performed at temperatures below this temperature. The limitation imposed on the low temperature method is in the properties of the electrolyte. At low temperatures, some electrolytes become too viscous to adequately wet the surface of the anode, particularly the surface in the pores or gaps of the anode. By initiating the process in a vacuum, the reduced wetting characteristics of a relatively high viscosity electrolyte can be partially compensated by forcing the electrolyte into the small holes. By paying attention to the properties of the electrolyte and developing low temperature electrolytes that provide good surface wetting properties at low temperatures, the present method can be carried out at increasingly lower temperatures.

  In the embodiment of the method of the invention shown in FIG. 1, the anode is immersed in an electrolyte forming bath containing the forming electrolyte. The anodization step is performed as discussed herein below. During the anodization process, the temperature of the forming electrolyte is accurately maintained at a temperature of 40 ° C. or lower.

  In another embodiment of the method of the invention shown in FIG. 2, the anode is immersed in an electrolyte forming bath containing the forming electrolyte, and the anodization step is performed at a constant current until the target potential is reached. After reaching the target potential, the anodizing step is performed at the target potential or at a constant potential until the current drops below a predetermined level. During the anodization process, the temperature of the forming electrolyte is accurately maintained at a temperature of 40 ° C. or lower.

  In another embodiment of the method of the present invention, temperature management is accomplished by circulating a cooled forming electrolyte stream to provide a cold stream of forming electrolyte. This cold stream is returned or recycled into the forming bath. Referring to FIG. 3, in this example, the valve metal anode is immersed in an electrolyte forming bath containing the forming electrolyte. An anodizing step is performed to form an anodic oxide on the surface of the anode. The anodization process is performed at a constant current until the target potential is reached and continues at the target potential until a predetermined stop current level, i.e. this level is reached. During the anodization process, the forming electrolyte is heated by dissipating heat in the anode by electrical power. In order to thermally control the temperature of the forming bath, Applicant circulates the forming electrolyte stream 41 from the forming bath in tank 2 as shown in FIG. The cold stream 41 is returned to the forming bath. During the anodization process, the forming electrolyte stream 41 is cooled and recirculated to accurately maintain the temperature of the forming bath at a temperature of 40 ° C. or lower.

  D. if desired M.M. As described by Smith et al. (Pages 1264 to 1270 (1963) of Journal of Electrochemical Society No. 110 (12)), the anode is removed from the forming tank 20, the formed electrolyte is washed away, and the oxygen-containing atmosphere is removed. After the anode has been heat treated or annealed at a temperature of about 350 ° C., the anodic oxide may be modified somewhat by performing another anodizing or reanodicing step. The purpose of the heat treatment and subsequent re-anodization is to improve the dielectric properties of the anode. Another purpose of the heat treatment is to widen the oxide cracks and cracks and repair these cracks and cracks in one or more subsequent reanodization steps.

  In order to perform re-anodization, the anode is again immersed in the forming electrolyte and another anodization step is performed. At this time, the potential is constant until the stop current level is reached. Preferably, the reanodization is performed at a temperature slightly above the planned operating temperature of the device. For devices operating at body temperature, the temperature of the electrolyte bath for re-anodizing is preferably about 40 ° C. Although not preferred, reanodization can be performed at both cold and hot non-operating temperatures. Several such annealing and re-anodizing steps may be added. Preferably, one such step is added after the target potential has been reached and the formation current has dropped below a threshold of about 0.05 mA to 0.5 mA per gram of anode weight.

  Referring again to FIG. 4, this figure shows a block diagram of another embodiment of the method of the present invention for forming a high voltage anodic oxide on a valve metal anode. In the method of this embodiment, an electrolyte formation tank 20 is provided. Tank 20 is configured to receive one or more anodes and includes an electrolyte forming bath that includes a forming electrolyte. In addition, an electrolyte circulation subsystem is provided for circulating and cooling the forming electrolyte. One or more anodes, i.e. valve metal anodes, are immersed in the forming electrolyte. The forming electrolyte is circulated from the forming bath through a circulation subsystem to provide a cold stream of forming electrolyte. A predetermined potential is applied to one or more anodes and ramped to a target voltage at a constant current until the target potential is reached. After reaching the target potential, the anodization process is continued at the target potential until the forming current drops below a predetermined stop current level.

  During the application of the potential, the flow and temperature of the cold flow of forming electrolyte is adjusted so that the temperature of the forming electrolyte in the forming tank is accurately maintained at a temperature of 40 ° C. or lower. In this and other embodiments of the method of the present invention, the temperature can be accurately controlled by any of the various techniques disclosed herein. This includes recirculation of the cold stream 41, circulation of cooling fluid through a suitably shaped tank plenum, or heat transfer to a temperature controlled environment or medium.

  As discussed above, for one or more anodes, a re-anodization step may be performed after one or more heat treatment steps or annealing steps. Preferably, one such annealing step and re-anodizing step is performed after one or more anodes have reached the target potential and the forming current is, for example, about 0.05 mA to 0.5 mA per gram of anode weight. This is done both after falling below a predetermined level.

  The above-described embodiments of the method of the present invention have been provided as non-limiting examples. A detailed description of these steps herein or in the claims does not imply that these steps were provided in the only possible sequence. This is because the sequence of specific steps may be altered and still fall within the intended scope of the claimed invention.

  As described in the previous discussion of the method, the anodization step is performed by applying a potential that increases to the target potential at a constant current to one or more anodes until the target potential is reached. After reaching the target potential, the anodization process is continued at the target potential until a predetermined stop current level is reached. This can be done by the prior art as illustrated in FIG. 8 or by the improved pulse technique of US patent application Ser. No. 10 / 058,437 as illustrated in FIG. This improved pulse technique also assists in thermal management. The advantages of the present invention can be realized with either technique.

  With reference to the discussion and claims herein, the phrase “constant current” refers to a continuous current (see FIG. 7) or a pulsed current with a constant pulse height (see FIG. 8). ) Should be understood to be used in connection with any of The method of the present invention may be implemented applying any of these current forms. Further, the term “stop current level” relates herein to the current drop level at the end of formation, ie the current drop point. As a non-limiting example, the desired predetermined level may be 1/10 or about 1/100 of a constant current applied in some applications. This predetermined level may vary depending on the application. These levels are readily determined by those skilled in the art.

  FIG. 7 shows a typical formation trace obtained with a conventional formation protocol. The current is set to a constant level and slowly increases until the voltage reaches the target formation potential (Vf). The current drops rapidly after reaching the formation potential. Small changes to this protocol are described in the above-cited US Pat. No. 6,231,993. This patent stipulates that the voltage must be turned off approximately every 3 hours to allow cooling and diffusion of the electrolyte.

  FIG. 8 schematically shows current and potential traces by applying a pulsed forming potential. The formation waveform is defined by the waveform period t. The waveform period t may be constant or variable over the formation cycle and duty cycle, and may be constant or variable over formation. The ratio of the pulse width of the applied current or potential expressed as a percentage of the time width to the waveform period t is the load period d. Preferably, the duty cycle d is high during the initial formation phase where the potential and current pulse widths are large. The duty cycle d, and the corresponding applied potential and current pulse widths, decrease as the formation potential increases toward the target formation potential and until the target potential is reached. It can be seen that the height of the constant current pulse drops when it reaches Vf.

  The forming method of the present invention in conjunction with forming potential and current traces as shown in either FIG. 7 or FIG. 8 provides comprehensive and accurate thermal management when anodizing a sintered valve metal anode. This greatly eliminates anodization defects due to electrolyte residues and in situ deposition. This greatly improves the dielectric properties of the anode, i.e. the capacitance of the anode. The formation method is simply defined by a limited set of parameters that are easily adjusted to the various sizes of the anodes and their internal characteristics.

In accordance with the present invention, the protocol for forming a high voltage anode anode using pulse technology is characterized by the following parameters and is shown generally in FIG.
1. ) Target formation potential Vf
2. ) Formation current If
3. ) Formation frequency νf = 1 / t that defines a waveform period in which the formation potential is applied in pulses
4). ) A load period d of a rectangular shaped potential waveform defining a portion of the shaped potential waveform period in which a potential is applied to the anode and a forming current If is passed through the anode-electrolyte system.
5. ) Formation bath temperature Tf accurately maintained at 40 ° C. or lower for large high voltage electrodes

Case 1

  A set of eight capacitors was formed with the pulse forming technique shown in FIG. 8 and discussed hereinabove. The first through fourth anodes were processed with a prior art method system that did not actively control the temperature. This allows the bath temperature to vary during maximum power dissipation or to rise to 40 ° C. Nos. 5 through 8 were processed in a system in which the temperature of the forming bath was precisely controlled by the method of the present invention and the temperature was kept constant at 18 ° C. The other processing conditions are the same for all eight anodes except that the positive temperature control according to the present invention is used in the processing of anodes 5 through 8 and the temperature of the forming electrolyte is maintained at exactly 18 ° C. It is. For the four electrodes, the target potential is 260 V and the initial formation current is 275 mA. The forming frequency is about 0.2 mHz, and the load period is 95% to 75% depending on the power dissipation. Table 1 shows the capacitance enhancement observed with anodes formed in accordance with the present invention.

  As the data in Table 1 shows, forming the anode according to the present invention improved the capacitance compared to anodes formed according to prior art methods without thermal management. The improvement in capacitance is due exclusively to improvements in the method, including actively cooling the forming electrolyte bath and maintaining its temperature at exactly 18 ° C. The capacitance of the anode formed at 18 ° C. is 2% to 5% better than that formed under conditions where the temperature is increased to a maximum of 40 when maximum power is dissipated. This improvement in capacitance is obtained by comparing the difference between the 3rd and 7th anode capacitances and the difference between the 1st and 5th anode capacitances.

  It has been shown that anodizing a valve metal anode according to the principles described herein improves the capacitance compared to an anode fabricated according to prior art methods. This improvement in capacitance directly leads to an improvement in the energy density of the capacitor, which allows a small device to be designed as a whole. Smaller devices alleviate the side effects associated with device implantation and improve patient comfort.

All patents and publications disclosed herein are hereby incorporated by reference in their entirety by reference to these patents and publications.
The specific examples and examples above illustrate the anode forming method according to the present invention for an anode that can be used in a capacitor, particularly a capacitor incorporated in an IMD. Accordingly, other means well known to those skilled in the art or disclosed herein, as well as means that exist before the filing date of this application, and that will become later, depart from the present invention, ie, the claims. It should be understood that it may be used without doing so.

FIG. 1 is a block diagram showing the steps of one embodiment of the method of the present invention. FIG. 2 is a block diagram showing the steps of one embodiment of the method of the present invention. FIG. 3 is a block diagram showing the steps of one embodiment of the method of the present invention. FIG. 4 is a block diagram showing the steps of one embodiment of the method of the present invention. FIG. 5 is a schematic diagram of one embodiment of a system according to the present invention. FIG. 6 is a perspective view of a forming tank useful in the system of FIG. FIG. 7 shows the formation of a typical prior art in which the potential rises smoothly until the target potential is reached, then held constant at the target potential for a predetermined holding time, and the current becomes increasingly smaller during this holding time. It is a graph of a trace. FIG. 8 is a graph of the formation trace obtained using the pulsed formation potential.

Explanation of symbols

10 System 20 Electrolyte Formation Tank 21 Lid or Cover 22 Fluid Inlet 24 Fluid Outlet 30 Electrolyte Subsystem 32 Heat Exchanger 34 Cooling Unit 36 Pump 38 Pipe or Hose

Claims (27)

A method of forming a high voltage anodic oxide on a valve metal anode comprising:
Immersing the valve metal anode in an electrolyte forming bath containing the forming electrolyte;
Carrying out the anodizing process;
Accurately maintaining the temperature of the forming electrolyte in the forming bath at a temperature of 40 ° C. or lower during the anodizing step. A method of forming a high voltage anodic oxide on a valve metal anode comprising:
Immersing the valve metal anode in an electrolyte forming bath containing the forming electrolyte;
Performing an anodizing step at a constant current until a target potential is reached, then at the target potential until the current drops below a predetermined stop current level; and
Accurately maintaining the temperature of the forming electrolyte in the forming bath at a temperature of 40 ° C. or lower during the anodizing step. A method of forming a high voltage anodic oxide on a valve metal anode comprising:
Immersing the valve metal anode in an electrolyte forming bath containing the forming electrolyte;
Performing an anodizing step at a constant current until a target potential is reached, then at the target potential until the current drops below a predetermined stop current level; and
Circulating the forming electrolyte stream from the forming bath through a heat exchanger to provide a cold stream of the forming electrolyte;
The temperature of the forming electrolyte in the forming bath is accurately maintained at a temperature of 40 ° C. or lower by introducing a low temperature flow of the forming electrolyte into the forming bath during the anodizing step. And a method comprising: A method of forming a high voltage anodic oxide on a valve metal anode comprising:
Providing an electrolyte forming tank with an electrolyte forming bath configured to receive one or more anodes and including a forming electrolyte;
Providing an electrolyte circulation subsystem for circulating and cooling the forming electrolyte;
Immersing one or more anodes in the forming electrolyte;
Circulating the forming electrolyte from the forming bath through the circulation subsystem to provide a cold stream of the forming electrolyte;
Applying a predetermined potential to the one or more anodes and increasing the potential to a target voltage with a constant current applied until the target potential is reached;
Continuing to apply a potential of the target potential to the one or more anodes until the current drops below a predetermined stop current level;
Adjust the flow rate and temperature of the cold stream of the forming electrolyte so that the temperature of the forming electrolyte in the forming tank is accurately maintained at a temperature of 40 ° C. or lower during the application of potential. And a method comprising: The method of claim 4, comprising:
The tank further includes a plurality of anode forming slots, and at least one anode is immersed in at least one of the plurality of anode forming slots.   The method of claim 1, wherein the temperature of the forming electrolyte is accurately maintained at or below 30 ° C.   The method of claim 1 wherein the temperature of the forming electrolyte is accurately maintained at or below 20 ° C.   The method of claim 1, wherein the temperature of the forming electrolyte is accurately maintained at 10 ° C. or lower.   The method of claim 1, wherein the temperature of the forming electrolyte is maintained at a temperature between 10 ° C. and 40 ° C. or less.   The method of claim 1, wherein the temperature of the forming electrolyte is maintained at a temperature between 0 ° C and 40 ° C. The method of claim 1, further comprising:
Removing the anode from the electrolyte forming bath;
Applying a heat treatment to the anode;
Re-immersing the anode in the forming electrolyte;
Carrying out a second anodizing step while accurately maintaining the temperature of the forming electrolyte in the forming bath at a temperature of 40 ° C. or lower. The method of claim 4, further comprising:
Removing the one or more anodes from the electrolyte forming bath;
Applying a heat treatment to the one or more anodes;
Re-immersing the one or more anodes in the forming electrolyte;
Circulating the forming electrolyte from the forming bath through the circulation subsystem to provide a cold forming electrolyte stream;
Applying a predetermined potential to the one or more anodes and increasing the potential to a target potential at a constant current;
Continuing to add the potential at the target potential until the current drops below a level at a predetermined stop;
Adjusting the flow rate and temperature of the cold forming electrolyte stream such that the temperature of the forming electrolyte in the forming tank is accurately maintained at a temperature of 40 ° C. or lower during the step of applying the potential; , Including methods.   The method of claim 1, wherein the anode is a tantalum anode.   A tantalum anode formed by the method according to any one of claims 1 to 4. An electrolyte bath system,
A tank formed with an inlet and an outlet, with an electrolyte forming bath containing a forming electrolyte, formed to receive one or more anodes;
An electrolyte circulation subsystem connected to the tank in flow communication and configured to receive an electrolyte flow from the outlet for lowering the temperature of the electrolyte flow and returning the electrolyte flow to the inlet; , Including bath system. An electrolyte bath system,
A tank having a lower level and an upper level in flow communication with the lower level, the lower level having an inlet configured to receive an electrolyte flow into the tank, the upper level being A plurality of anode-forming slots formed in the upper level, the slots being sized to receive at least one anode. Each of the slots has an opening through which electrolyte flows from the lower level into the upper level; and
An electrolyte circulation subsystem coupled to the inlet and the outlet. The bath system according to claim 15,
The electrolyte circulation subsystem comprises a heat exchanger coupled to a cooling unit and at least one pump for circulating an electrolyte between the tank and the electrolyte circulation subsystem. The bath system according to claim 15,
The electrolyte circulation subsystem includes:
A heat exchanger,
A cooling unit coupled to the heat exchanger;
At least one pump for circulating electrolyte between the tank and the circulation subsystem;
A bath system comprising at least one pump or blower for circulating a cooling fluid through the cooling unit. The bath system according to claim 15,
A bath system wherein the tank is an enclosed housing formed with a lid, the system further comprising a vacuum unit for generating a vacuum in the tank.   16. The bath system according to claim 15, further comprising a vacuum unit configured to generate a vacuum in the tank.   16. The bath system according to claim 15, further comprising a vacuum unit configured to generate a pressure differential that can force the electrolyte into a small hole or gap in the anode. The bath system according to claim 15,
The bath system wherein the tank further comprises a plurality of fins or a plurality of fans for heat dissipation.   The bath system according to claim 15, further comprising an electronic control unit.   16. The bath system according to claim 15, further comprising an electronic controller, wherein the controller is equipped and formed to regulate either or both of the electrolyte circulation rate and / or heat transfer rate. Bath system.   16. The bath system according to claim 15, further comprising an electronic controller, wherein the controller is equipped and formed to regulate electrolyte circulation rate, heat transfer rate, and cooling fluid circulation rate. system. In the electrolyte bath system,
A tank with an electrolyte forming bath containing a forming electrolyte, the tank being configured to receive one or more anodes, said tank forming a plenum through which cooling fluid can be circulated A tank having inner and outer walls spaced apart, an inlet for receiving cooling fluid into the plenum, and an outlet for discharging the cooling fluid from the plenum;
A cooling fluid circulation subsystem coupled in flow communication with the inlet and the outlet. The bath system according to claim 18,
A bath system wherein the heat exchanger includes a wall portion filled with a liquid in a tank containing a forming electrolyte.

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