SMDs in Medical Electronics: Just What the Doctor Ordered


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Craig Hunter, Vishay Intertechnology, discusses the medical electronics sector. Recently, component manufacturers have stepped up interest in medical applications. The reasons aren’t difficult to discern. As reported recently by Databeans, there is no shortage of demand for better and more innovative medical equipment, and thus medical electronics has come to represent the fastest growing segment of the industrial market for semiconductors. Secondly, this growth has been quite robust with respect to the worldwide economic downturn. If that phenomenon seems counterintuitive, then consider that one of the key trends in reducing healthcare costs has been to shift the focus of care from hospitals and doctors’ offices to patients’ homes. This could only happen with advances in medical technology, mainly enabled by advances in the performance and reliability of electronic components. The general trend in the converging computing, communications, and consumer (3C) entertainment markets is toward surface mount devices (SMDs). This move is fueled by the need to shrink footprints and reduce the parasitics and quality problems associated with wire mounting leads. Both of these improvements are useful in medical applications, particularly those associated with implanted, wearable, or portable equipment. Other key drivers are lower power consumption and improved cost-effectiveness of equipment and the manufacturing process. It is not surprising to find a number of components that are equally at home in commercial and medical applications. Applications such as medical imaging use the same types of FPGAs, ASICs, DSPs, and embedded micros as systems in the industrial end-market category. Certain medical applications impose inherent restrictions on component types. For example, use of infrared (IR) as a data-transfer medium remains preferable in medical settings, thanks to the high security capabilities compared to RF transmission. Therefore, the same infrared transceivers used for Point & Pay financial messaging are a popular solution for uploading data from medical instrumentation to monitoring PCs. Non-magnetic components are obviously desirable for magnet-based systems like MRIs; resistors and multilayer ceramic capacitors (MLCC) with non-magnetic terminations are a direct response to this need. The closer electronic components come to life-support applications, the more they are distinguished from normal commercial components by heightened standards for reliability. It is not unusual to find the same components being used in both hi-rel military/aerospace and medical applications. In the case of tantalum capacitors, for example, the high-reliability medical-grade devices are distinguished by the use of tantalum powder that is specifically chosen for its low leakage current (DCL) characteristics. Leakage must be minimized at any cost to ensure reliable operation. Likewise, new surface mount MLCCs that are specially designed to prevent surface arc-over or minimize internal cracks during the manufacturing process/handling will add reliability to any electronic product but are particularly desirable for medical applications. This is an emerging, high-value market; another aspect of surface mount components in this area is the development of custom devices to meet very specific requirements. For example, a drug-delivery system that needs to be very small to allow ingestion may require relatively small batches of capacitors to be manufactured with different X, Y, and (more often) Z sizes. The cost implications of this customization are justified by the high reliability needs of the application. In some cases, the major distinction between commercial and high-reliability medical devices may be one of process flows or testing, in which devices destined for medical applications are subject to more intense quality control (QC) measures at every stage of the manufacturing process. New-generation medical MOSFETs are a good example of such an approach. Mechanical tests performed once a day for commercial MOSFETs (such as ball sheer, wire pull, and wire loop) are performed on each lot in the medical flow. Electrical test screening using part average testing (PAT) and Maverick lot Statistical Yield limits (SYL/SBL) must also be performed on every lot. In addition to this enhanced quality sampling, plans will be used to achieve quality levels reaching 0.04%. Applying more stringent production flows and testing methods has yielded new component ranges, enabling exciting medical device developments in the areas of medical implantable systems, drug delivery systems, defibrillators, pacemakers, and hearing aids. Craig Hunter is an SMT Editorial Advisory Board member and director, global Internet marketing at Vishay Intertechnology Inc. Contact him at craig.hunter@vishay.com. Recent Articles by Craig Hunter: With Electronics, You Can Never Be Too Thin SMT Components Toughen Up for Rugged Applications Embracing Brand Value and New Web Technologies

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