PASSIVE COMPONENT INDUSTRY SEPTEMBER/OCTOBER 2001
By Dennis M. Zogbi
Over the years, Paumanok Publications, Inc., has conducted in-depth research into a variety of specialty capacitor markets, including applications for detonators, missile power- up, downhole drilling, undersea cable repeaters, and medical implants.
In all specialty capacitor markets, typically, price is secondary to performance and reliability; manufacturers of capacitors used in these markets must spend much more money for testing of such devices, as compared to capacitor applications for bulk bypass and decoupling, and filtering markets.
Other commonalities shared by specialty capacitor markets are low-volume demand, considerably high unit value, and usually excellent profit margins. While testing methods may vary among end-use market segments, all tend to include requirements that test their devices for or under such unique conditions as extreme h e a t , r a d i a t i o n , corrosion resistance, vibration freq u e n c y, a n d , of course, high reliability under thousands of hours of operation.
Implantable defibrillators comprise one of the most fascinating specialty capacitor markets. While sharing similarities with other specialty capacitor markets, the implantable defibrillator market is unique with regard to business climate and a lack of competition. For years, many companies have been afraid to venture into the implantable defibrillator capacitor market, because a capacitor failure can lead to significant lawsuits that could drive manufacturers out of business. The lack of competition has slowed the growth of technology in the field , leaving many defibrillator manufacturers to serve as sole-source vendors of the capacitors or as captive developers of the technology.
Implantable Defibrillator Capacitor Requirements:
Capacitors used in implantable defibrillators exhibit unique qualities: A combination of high voltage, high capacitance, and small case size confines the possible usable dielectrics to aluminum electrolytic. Implantable defibrillators require two 390-VDC, 200-μF capacitors per defibrillator to achieve the 30- joule, 750-volt, 10-millisecond pulse necessary to start the human heart. The normal load of the capacitor is 50 ohms, with a minimum requirement of 20 ohms. The capacitor energy is accumulated from a battery over a 10-second time period and released in a 10 millisecond flash. Certainly, one 750-volt capacitor could be used, but its size would restrict its use, especially with the trend to make smaller and thinner devices, requiring less invasive surgery. It is fascinating to note that between 1997 and 2001, the weight of an average implantable defibrillator has declined from a norm of 250 grams to about 120 grams; its volume has declined from 100 cubic centimeters to 70 cubic centimeters over the same time period. Capacitors still occupy about 30% of the volume of a finished defibrillator, which means that the capacitor has declined in volume from 30 cubic centimeters in 1996 to 21 cubic centimeters in 2001, representing a 30% volumetric reduction over four years. That drop translates into much smaller devices, making them surgically less invasive as well as expanding their usage globally.
Implantable Defibrillator Prices and Markets
Each aluminum electrolytic capacitor used in an implantable defibrillator sells for between $75.00 and $150.00, even though it costs about $0.05 to $0.25 per unit to wind the capacitor; each defibrillator uses two aluminum electrolytic capacitors (the price for an implantable defibrillator capacitor in 1993 was about $1.50 per unit, or the same price as a camera flash capacitor, which has a similar construction). Pricing became very high for these capacitors after Dow Chemical was required to pay substantial settlements for faulty breast implants, making the market too small for traditional capacitor suppliers, who preferred to give up the market rather than lose their businesses in a lawsuit. Also, a narrow vendor base and limited sources for the precise raw materials consumed in the capacitors precluded the competitive environment necessary to keep prices in check.
The world market for implantable defibrillator capacitors was an estimated $20 million USD in 2000, with approximately 160,000 capacitors placed in 80,000 implantable defibrillators. The implantable defibrillator capacitor market has grown approximately 20% per year since 1997. Each defibrillator requires two capacitors to achieve the 700 VDC required to start the heart.
Growth is expected to be rather substantial, averaging about 20% per year over the next five years, due primarily to the determination by the National Health Institute that implantable defibrillators save substantially more lives than does drug therapy.
Although there are many small suppliers of flash aluminum electrolytic capacitors for applications in camera flashes and strobe lights, t h e world leader is Rubycon Corporation of Ja p a n , w h i ch we estimate had $85 million in revenues from the flash capacitor market worldwide in 2 0 0 0 . Without exception, R u b y c o n manufactures the best flash capacitors in the world, according to their customers. T h e y maintain at least 70% of the camera flash market and 95% of the medical implant market for flash capacitors. U n f o r t u n a t e l y, other suppliers such as Nippon Chemi-C o n , N i ch i c o n ,E l n a , and Pa n a s o n i c, who have the tech n ical capability to compete in the medical implant market, h ave restricted their product lines to flash capacitors for the strobe and camera flash markets, choosing not to compete in the medical market because of the potential for l aw s u i t s, should their capacitors fail in operation.
Device Manufacturers’ Strategies
The major world manufacturers of implantable defibrillators include Medtronics, G u i d a n t / C P I , I n t e rmedics, and St. Jude/Ventritex. In 1997, faced with the prospect of a sole source for implantable defibrillator capacitors, these companies began looking for an alternative dielectric or to captively produce a device to compete with Rubycon’s.
St. Jude’s was the first company to bring medical implant
capacitor manufacturing technology in-house with the purchase of Maven Capacitor in Liberty, South C a r o l i n a , U S A . M aven Capacitor had the ability to not only produce defibrillator capacitors but also to etch its own photoflash capacitor foils. Guidant and Medtronics, the two market leaders, as well as others, also explored the possibility of bringing capacitor technology in-house, as did Wilson Greatbatch , the premier supplier of implantable defibrillator batteries, and a pioneer in the d evelopment of implantable defibrillator tech n o l o g y.
Gaps and Showstoppers in Captive Production
One of the most difficult aspects of capacitor production for implantable defibrillators is obtaining the correct raw materials required to produce photoflash-quality capacitors. Like the capacitor itself, it seems that access to raw materials is also sole sourced to Ja p a n . Photoflash anode and cathode foils differ from tradit i o nal capacitor foils insomuch as they require a porous rolled stock with 425 to 435 VDC forming voltage; t h e anode foil requires 0.8 μF to 0.9 μF of capacitance per cubic centimeter. Using Rubycon as an e x a m p l e, it is believed that its porous aluminum stock comes from Toyo A l um i n u m , w h i ch , in turn, is etched by Japan Capacitor Corporation (JCC). While it is likely that other companies s u ch as Satma (Pe chiney) and Becromal have the capability to produce their own photoflash foils, they target their products more toward the camera flash and strobe markets rather than the medical implant market, because they fear potential law s u i t s in the event of catastrophic device f a i l u r e.
Implantable defibrillator manufacturers also experimented with alternative capacitor dielectrics, with the strategy of developing a new type of defibrillator that was not reliant upon aluminum capacitor technology and Rubycon as the sole source supplier. The problem with developing an alternative dielectric was in accommodating the required combination of high voltage, high capacitance, and small size for the implantable defibrillator. Ceramics based on barium titanate technology, for example, had demonstrated the ability to store 12 joules per cubic centimeter and to obtain high volta g e s, but their low energy density in the finished c apacitor and their typical weight of 5.8 grams per cubic centimeter p r e cluded them from use in implantable defibr i l l a t o r s ; polypropylene and polyester, w h i ch are electrostatic dielectric materials like ceramics, had the same problem, wherein the proper voltage was obtainable, but the required capacitance or energy density was not. Electrochemical designs based on tantalum had the proper capacitance value, but lacked in terms of voltage. The same issues emerged regarding double-layer carbon s u p e r c a p a c i t o r s, w h i ch also provided the necessary c apacitance values, but voltages per cell were too small and discharge times too fast for carbon materials to handle.
Efforts for developing an alternative dielectric material for implantable defibrillator capacitors shifted towa r d creating a hybrid design, intended to marry one type of capacitor with another, thus capitalizing on the benefits while minimizing the shortcomings. Dave Evans of Evans Capacitor was the first to successfully demonstrate the possibilities of this approach . Evans joined an e l e c t r o chemical capacitor cathode (ruthenium on tantalum
foil) with an electrolytic capacitor anode (porous tantalum slug) to create a device with high capacitance and high single-cell voltage. That concept was ultimately l icensed by Wilson Greatbatch , who improved upon the t e chnology for use in implantable defibrillators. A e r o v o x , a leader in polypropylene capacitors for external defibrillators, has reportedly experimented with a hybrid device that combines an electrochemical capacitor cathode with an electrolytic anode.
Others are also developing various solutions to the problem. R i chard Wu of K Systems, in conjunction with the University of Cincinnatti and W r i g h t Patterson Air Force Base, has developed a diamond-like carbon film cap a c i t o r, wherein hydrocarbon atoms are deposited on aluminum foil via ion gun tech n o l o g y, after which , the foil is rolled into a capacitor. The result is a capacitor with a high voltage per cell (1.5 kV) and a capacitance value as high as 33 μF in a very small case size Also, it has been reported that Integral Wave Technologies of Fayetteville, Arkansas, has been awarded an SBIR contract for the development of its stacked capacitor design, based on deposited electrolytic metals on electrostatic film substrates. The stacked version of this capacitor offers high capacitance and high voltage per cell in a small, thin case size that is ideally suited for implantable defibrillator designs.
Interesting to note, many implantable defibrillator device manufacturers feel that a film dielectric approach may be the answer for the future well-being of implantable defibrillator capacitors. Some companies believe that if such films as PVDF and polycarbonate could be extruded thin enough, they could provide the capacitance, voltage, and discharge time required for use in implantable defibrillators in exceedingly smaller sizes.
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