Using etch resist patterns and formation for facilitation of laser cutting, particle and leakage current reduction

#The present invention is directed to etching anodic foil to be used in electrolytic capacitors and more particularly, to a method of etching of anode foil to produce higher capacitance foil with improved leakage current and deformation, and to an electrolytic capacitor incorporating the etched anode foil of the present invention for use in an implantable cardioverter defibrillator (ICD).

#Compact, high voltage capacitors are utilized as energy storage reservoirs in many applications, including implantable medical devices. These capacitors are required to have a high energy density since it is desirable to minimize the overall size of the implanted device. This is particularly true of an Implantable Cardioverter Defibrillator (ICD), also referred to as an implantable defibrillator, since the high voltage capacitors used to deliver the defibrillation pulse can occupy as much as one third of the ICD volume.

#Implantable Cardioverter Defibrillators, such as those disclosed in U.S. Pat. No. 5,131,388, incorporated herein by reference, typically use two electrolytic capacitors in series to achieve the desired high voltage for shock delivery. For example, an implantable cardioverter defibrillator may utilize two 350 to 400 volt electrolytic capacitors in series to achieve a voltage of 700 to 800 volts.

#The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

#FIGS. 1A and 1B show a schematic depicting masked tab areas relative to unmasked areas to be etched according to the present disclosure.

#FIGS. 2A and 2B show photographs of a masked tab pattern on a bulk metal foil according to the present disclosure.

#One aspect of the invention is directed to a process for etching an aluminum foil to minimize thermal oxidation and produce higher capacitance foil without sacrificing foil strength, to a process for creating an aluminum anode foil, and to an etched aluminum anode foil etched by such processes for use in an implantable cardioverter defibrillator (ICD).

#Embodiments of the invention are now described. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the invention. It will be apparent to a person skilled in the relevant art that this invention can also be employed in a variety of other devices and applications.

#According to the present invention, an anode metal foil to be etched is selected. Aluminum foil is preferred, because of its ability to produce a sufficient quality oxide layer, its conductive properties, and its wide commercial availability. However, other foils conventionally utilized in electrolytic capacitors could also be used, including tantalum, magnesium, titanium, niobium, zirconium and zinc. Preferably, a 100 to 125 micron thick, unetched, high purity (at least 99.98%) strip of aluminum foil with high cubicity, wherein at least 80% the crystalline aluminum structure is oriented in a normal position (i.e., a (1,0,0) orientation) relative to the surface of the foil, is used. Such foils are well-known in the art and are readily available from commercial sources.