Miniaturization of Connectors for the New High Speed Digital Electronics
Research, design and investment in Medical Electronics are focused heavily on the miniaturization of equipment, sensors and probes. Demand from hospitals, practitioners and patients for more functionality and increased portability has created a market for upgraded surgical, diagnosis and monitoring equipment. The push for shorter hospital stays has increased the need for portable monitoring equipment that travels with the patient after recovery and release. Doctors’ offices, neighborhood radiology examination offices and outpatient clinics are all benefiting from new electronic technologies.
This generation of planetary patient clinics offers services such as blood analysis, endoscope related procedures and minimally invasive ultrasound procedures in smaller localized facilities. Many procedures require catheters, probes or chips that touch the patient and/or patient fluids. Often, a portion of these products must be sterilized or discarded totally after use. Office diagnostics now include medical imaging beyond the old x-ray systems with portable ultrasound systems, optical inspection tools and electronic catheters. New laser skin enhancement systems are used in localized offices instead of being captive to the large hospital systems.
As a result of this dynamic change in the medical service system, a new focus is driven towards smaller, more portable and more capable equipment that can move from office to office within a service center. There is a need for more clarity, higher definition and more functions. To serve the practitioner and patient better and at a lower cost, highly reliable equipment, with significantly upgraded processing capability, is being developed. Portability and size reduction of the instruments and equipment are considered highly important. To accomplish this, every portion of the equipment design is considered a candidate for miniaturization.
Fortunately, an early model existed for the evolution of miniature electronics from similar industry challenges. Cell phones, laptop computers and digital cameras all contain high performing chip technology that serve a growing demand and a growing appetite for more functions. Portable test equipment used in various sectors such as telephones and the petroleum industry require increased testing and diagnostic functions, in addition to increased reliability and ruggedness for field applications. GPS modules, missile guidance systems and portable military equipment used on today’s modern soldier also pushed the electronics industry towards compact miniaturization. The answer emerged with the C-MOS (Complementary Metal-Oxide-Semiconductor) chip technology. C-MOS techniques have allowed significant increases in function and processing capacity while simultaneously increasing the density, reducing size and weight and even offering more rugged, portable electronic products.
Early adopters in the medical field included pacemaker manufacturers that used C-MOS technology to combine analog and digital signals into a single-chip pacemaker. This reduced size and weight while increasing the analysis and control functions of the pacemaker. Soon, digital medical instruments from stethoscopes to defibrillators emerged using similar chip techniques as previous military and consumer products. Since then, new medical processing chips, instruments, connectors, probes and sensors have all begun an evolution towards miniaturization.
Silicon chip designers have evolved to serve the medical industry, primarily with C-MOS and related technologies. In the past, electronic circuits using analog technology or even earlier digital chips required relatively high voltage and used more electrical current. The instrument boxes began with large power supplies and large wire systems running circuitry within the instrument to feed the electricity-hungry modules inside. Wires had to be large enough to handle the current flow and insulators had to be thick enough to keep circuits from shorting to one another. Cables were designed to handle analog sine-wave signals for long runs and were also shielded to reduce electrical noise inside the instrument.
Today’s mini-medical systems on a chip, however, have changed the rules and electrical demands in the whole instrument. New medical chips do not require the same level of support and protection, however, the signals are predominately digital. Voltages are usually regulated from 12 volts down to as low as 3 volts. Current flows have dropped from nearly 3 amperes to ranging in the 100 mill-amp range and lower. Power supplies or batteries are dramatically smaller and lighter than in the past. Interconnection systems within the instruments can be significantly reduced in size. In addition, wiring can be nearly half as large with plenty of capacity for current flow. With lower voltages, the insulator materials in circuits can be significantly smaller and more compact. As a result, miniature connectors and smaller wires solve an additional size and reliability problem for medical instruments. High reliability, ruggedness and long life can be achieved if designers use the high reliability standards previously proven in other high-technology applications, such as military and aircraft circuitry.
Medical electronic subcontractors and component manufacturers have followed suit. Cable and connector manufacturers, such as Omnetics, have developed Micro-miniature and Nano-miniature connectors specifically for the medical industry. Using wiring made up of 30 awg. conductors (approx. .012 thousands of an inch in diameter), cables have become more flexible and can hold more signals in smaller and lighter interconnection systems. The mating connector designs have reduced sizes from the older 100 mil. size connectors, often used in household computer towers, down to the miniaturized connector systems at .050” (1.3mm) and .025” (.625mm) spacing.
These miniature connectors using smaller wiring systems can handle increased chip function in about one-fourth the space of previous systems. Portable devices can use chips right at the probe tip and be connected by miniature cable to the monitoring instrument. They can be easily disconnected for cleaning or disposal using miniature in-line connectors designed specifically for the instrument.
Medical instrument quality and reliability are clearly required in the new miniaturized connectors. To achieve that goal, manufacturers have selected the highest reliability elements for use in most medical connectors. The spring pin and socket system has proven reliability over wide ranges of shock, vibration and thermal changes. Made of BeCu (beryllium copper) with high tensile strength (17,200ksi), it manages to withstand the rigors of use and abuse often experienced in the hurried business of patient service. Pin and socket elements selected should also pass plating tests specified in Mil. B488-type II, Code C class 1.27. This requires a strong nickel plate barrier that is coated with 50 micro-inches of gold. When placed into miniature insulator housings, molded from LCP (Liquid Crystal Polymer), the connector remains at the highest level of reliability testing in medical, military and aerospace industries.
The assembly often consists of Teflon® insulated wiring that is carefully laser stripped (to avoid nicking miniature wiring) and crimped into the back section of the pin system. The pin-and-wire set are then inserted into the LCP insulator and fixed with epoxy in place. An “over-molded” shell that can be customized to the designer’s criteria completes the assembly. Alternately, the pin and wire set are inserted into a metal housing to finalize the miniature medical connector. This high-reliability assembly method is sometimes called “crimp-and-poke” technology. Benefits of this assembly process are precision, tight tolerances and high-quality miniaturization that greatly exceed the performance of single spade pins in lower quality plastic housings.
Connector Design Engineers begin with careful materials selection to match the specific medical service or application. The first requirements are to use Medical Grade materials and avoid those used in standard consumer products. Low cost is a plus, but inferior molding and using materials that can grow or host bacteria can lead to serious problems. Designers must focus on disinfection or sterilizable polymers as well as the look and feel of the connector housing and cable jacket. Cable ruggedness must work in hand with limpness and flexibility, while performing the signal management functions on the inside. Strong design systems try to match the need for technical requirements with the chance to optimize cost and price of the eventual products.
The medical electronics market is expanding rapidly and is supported by the use of modified or integrated standard connectors. Micro-miniature and Nano-miniature connectors can now be integrated into the design of medical instruments during early design stages. Connector solid model designs can be directly interfaced on-line by equipment designers to adjust shells and insulators to fit into handles, probes or custom mounted into instruments. This allows better fit and use of instrument in many design forms. Connectors are often “built-in” to the housing of a medical diagnostic device to provide a docking station and charging of the storage battery inside the instrument. Other connectors are built into catheter probe heads that allow the device to be attached for use and then disconnected for disposal or sterilization.
The evolution of a new connector industry: At the turn of the millennium, only a small handful of suppliers offered higher reliability connectors sized at the .635mm pitch configuration. Now, nearly every connector cable harness supplier offers some form of Nano connector in line with miniature medical electronic cables. SMT technology has also adapted to handle very tight pitch surface mounting to printed circuit boards for the tiny connector mounting leads.
According to a recent study by research firm MarketsandMarkets, the global medical electronics market was valued at USD 3 Billion in 2015 and is expected to reach USD 4.41 Billion by 2022, at a CAGR of 5.4% during the forecast period. A reflection of this is the massive growth in design teams, startup companies, and NIH-funded projects in university incubators that have sprung up over the past decade alone.
To glimpse the enormity of new technology for medical applications, one can conduct a simple search in Cannon Corporation’s annual Medical Device Register and sort through the NAICS listings. Using only the NAICS 334510 and 339112 groups, there are thousands of electro-medical and electrotherapeutic apparatus being designed with the new digital electronic systems, such as magnetic resonance imaging equipment, medical ultrasound, electronic endoscopic, surgical ophthalmic, catheters etc. Each of these systems use miniature cables and connectors to supply data to and from the instrument to the data acquisition probe or detector system.
One good example of a medical cable and connector supplier can be a reflection of many. Omnetics Connector Corporation, for example, built its strength on a focus of high-reliability and miniaturization. Omnetics also responded to the change in the military/aerospace industry and cut through the rigors of specifications and testing. In addition, Omnetics followed design and manufacturing down into the Nano-interconnection foot print. The company learned the quality control and manufacturing standards needed to continuously supply medical component level performance and reliability. But Omnetics went beyond that point and became a leader in custom design to meet new sizes and shapes demanded by the miniaturization of digital medical apparatus.
Omnetics provides a family of simple, standardized miniature circular connectors that can be fit into the mold of probes or sensors to reduce size and cost of the instrument while retaining high reliability. An additional benefit of the solid model design interface is that it is quick and shortens prototype cycles.
These new miniaturized connectors match up perfectly with the evolution of medical electronics, support instrument portability and size reduction while retaining the highest reliability standards expected for medical services. The miniature medical circular connectors, the “Bi-Lobe” (Nano-miniature rectangular connectors) and the newest Nano-sized circular connectors are serving the medical instrument market well. They help solve miniaturization and other common design challenges by providing new methods for addressing data-acquisition, sample collection and even therapy by delivering simple, comfortable cable systems connected to professional looking connectors to the instrument. Omnetics connectors also assist inside the instrument design by allowing circuits and interconnect systems to be smaller and attachable during the modular assembly process.
