Methods of manufacturing a hermetically sealed wet electrolytic capacitor and a hermetically sealed wet electrolytic capacitor

Methods of manufacturing a hermetically sealed wet electrolytic capacitor and a hermetically sealed wet electrolytic capacitor are described. A method of manufacturing a wet electrolytic capacitor includes forming a cathode of the capacitor by forming a case comprising a metal substrate, the metal substrate having an alloyed surface, depositing a smooth film comprising palladium and copper as a tacking layer on the alloyed surface of the metal substrate, and depositing a rough, high surface area layer on the tacking layer to achieve a high capacitance cathode. A first terminal is electrically connected to the cathode. An anode is formed. A second terminal is electrically connected to the anode. An electrolytic solution is disposed within the case, and the case is hermetically sealed.

FIELD OF THE INVENTION

The present invention relates to capacitors, and more specifically to a capacitor suitable for use in medical applications such as implantable cardioverter defibrillators.

BACKGROUND

Capacitors are used in a wide range of electronic applications. Certain applications require a capacitor which is capable of a rapid electrical charge to a pre-determined voltage and, once charged, is also capable of delivering sizeable pulses of energy. One example of such an application is in implantable devices. In such an application, it is also important that the capacitor be compact in size and highly reliable.

Thus, what is needed is a capacitor suitable for use in applications, such as implantable cardioverter defibrillators, where reliability and performance are provided in a small size.

SUMMARY

It is a further object, feature, or advantage of the present invention to provide a capacitor suitable for use in implantable devices.

A still further object, feature, or advantage of the present invention is to provide a capacitor that is capable of a rapid electrical charge to a pre-determined voltage and, once charged, is also capable of delivering sufficient pulses of energy to restore the normal function of a patient's heart when used in implantable cardioverter defibrillators (ICD).

Another object, feature, or advantage of the present invention is to provide a capacitor which is efficiently constructed and shaped to fit into the limited volume available within an ICD.

Yet another object, feature, or advantage of the present invention is to provide a capacitor with high performance and high reliability.

One or more of these and/or other objects, features, or advantages of the present invention will become apparent from the specification and claims that follow.

According to one aspect of the present invention, a hermetically sealed wet electrolytic capacitor is provided. The capacitor has a hermetically sealed case that encloses a cathode, an anode, an electrical insulator between the anode and the cathode and an electrolytic solution. A first terminal is electrically connected to the anode and a second terminal electrically connected to the cathode. The hermetically sealed wet electrolytic capacitor is able to provide a pulse delivery equal to at least 80 percent of the stored energy.

According to another aspect of the present invention, the capacitor's cathode includes a metal substrate having an alloy layer formed with a noble metal and a noble metal/base metal electrode element layer electrochemically deposited thereon, and the electrolytic solution has a conductivity between 10 and 60 mS/cm.

According to another aspect of the present invention, a method of manufacturing a capacitor is provided. The method includes hermetically sealing a case containing an electrolytic solution having a conductivity between 10 and 60 mS/cm. The method further includes electrically connecting a first terminal to an anode, the anode being insulated from a cathode. The method further includes electrically connecting a second terminal to the cathode. The cathode is formed from a metal substrate having an alloy layer formed with a noble metal and a noble metal/base metal electrode element layer electrochemically deposited thereon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is now described with respect to a particular embodiment. That which is shown is merely for purposes of illustration and example, and one skilled in the art will understand that the present invention contemplates other options, alternatives, or variations.

FIG. 1illustrates one embodiment of a capacitor10of the present invention. Although shown in a semi-circle shape, the capacitor10need not have such a shape. This particular shape is merely an example. InFIG. 1, a hermetically sealed wet electrolytic capacitor10is shown. The capacitor10has a hermetically sealed case12. The capacitor10has a cathode18and an anode16. One example design for an anode16would comprise sodium reduced capacitor grade tantalum powder pressed to a green density of between 5.0 and 7.0 grams/cc then vacuum sintered between 1450° C. and 1650° C. Powder, press and sinter conditions may be varied to attain the requisite capacitance. Formation of the anode should be in an electrolyte capable of sustaining the voltage necessary for the required oxide thickness.

An insulator14, (preferably, but not required, comprising one or more layers of a polymeric material), is positioned between the anode16and the cathode18to electrically insulate the anode16from the cathode18. An electrolytic solution22is disposed within the hermetically sealed case12and surrounds both the cathode18and the anode16. The electrolytic solution22preferably comprises a gel which includes DI water, organic and inorganic acids and an organic solvent. The constituent components of the electrolytic solution22may be admixed in a variety of concentrations to provide conductivity within a preferred range between 10 and 60 mS/cm. One example of such an electrolytic solution22would be:

65-80% DI water

The cathode18is formed from a metal substrate20having an alloy layer24formed with a noble metal and a noble metal/base metal electrode element layer26electrochemically deposited on the alloyed surface from a solution of the metal salts. One example design for the cathode18may be a mixture of Pd and Cu electrodeposited on a Ti—Pd alloy. To increase adhesion of the cathode18to the alloyed substrate, an initial smooth film of Pd—Cu may be electrodeposited as a tacking layer28. A rough, high surface area layer29can then be deposited on top of the tacking layer to achieve a high capacitance cathode18.

The metal substrate20of the cathode18can be formed of a valve metal. Examples of such valve metals include tantalum, niobium, hafnium, vanadium, zirconium, titanium or any of their alloys. The metal substrate20may have any number of shapes or configurations, including a planar or cylindrical shape. The metal substrate20may be a liner of any suitable shape and may represent a part of the capacitor case12. Such a construction of the cathode18results in high cathode capacitance which assists in efficiently delivering energy stored in the capacitor10to a load.

A first terminal30is shown extending through a spacer32. The first terminal30is electrically connected to the anode16. A second terminal36is electrically connected to the cathode18.

FIG. 2illustrates one embodiment of an implantable cardioverter defibrillator (ICD) device40. The device40includes the capacitor10ofFIG. 1(with a first terminal30and a second terminal36), and a control circuit42, which is electrically coupled to the capacitor10, a detector43and a battery44. The capacitor10is configured to provide a pulse delivery of at least 80 percent, (but preferably greater than 87 percent), of stored energy between the first and second terminals30,36. The detector43monitors a patient's condition and provides this patient data to the control circuit42. The control circuit42monitors the information from the detector and upon detection of an anomaly or a critical condition, (which may be defined as one or more predetermined parameters that have exceeded one or more predetermined thresholds).

By way of example, the detector43may detect electrical activity in the heart of a patient and forward this data to the control circuit42. The control circuit42monitors this electrical activity and if it drops below a certain electrical level, or if the electrical activity becomes irregular (as happens with an arrhythmia), initiates delivery of an electrical shock.

The battery44may be used to charge the capacitor10and to power the ICD device. The charging of the capacitor10may be constant (to counter the effects of charge leakage), such that the capacitor10is always ready for discharge; may be periodic (i.e. charging at predetermined intervals to keep the charge level of the capacitor10above a predetermined threshold); or may be on demand, such that when the onset of an anomaly is detected, the battery44is used to charge the capacitor at that time.

In the application of an ICD device40, the capacitor10performs the function of delivering electrical shock therapy into the heart of a patient when a control circuit42of the ICD device40detects an anomaly or a critical condition in the patient. The capacitor10allows the capacitor to be capable of providing a rapid electrical charge to a pre-determined voltage, and thereafter delivering one or more pulses of sufficient energy to restore normal functions of a patient's heart.

The capacitor10as shown inFIG. 1is efficient in nature and highly compact such that the capacitor10is constructed and shaped to fit within a limited volume within an ICD device40. Preferably, the size of the capacitor10is 1.5-3.0 CC, and comprises a half-moon shape as shown inFIG. 1, although this should not be construed to be limiting to the present invention. The capacitor10is able to conform to any size and shape in order to fit the particular configuration demanded by the person within which it is being implanted.

In order to support the application of an ICD device40, the capacitor10is able to supply a minimum of 9 J, (but preferably 12 J), upon demand. The amount of energy actually delivered is determined by the control circuit42.

A hermetically sealed wet electrolytic capacitor has been described. The present invention is not to be limited to the specific embodiment shown or described herein as the present invention contemplates variations in the size and shape of the capacitor, variations in the materials used, and other variations, alternatives, and options as would be apparent to one skilled in the art.