Connector Plating, Materials, and Manufacturing Considerations for
Medical Equipment
By Gilles Parguey, Product Manager, C&K Components

Connectors in medical equipment must be highly reliable (zero defects), while at the same time meeting stringent requirements for patient safety and harsh environmental conditions. Often, connectors must be able to withstand extremely high or low temperatures—extremes of up to 200+ degrees Celsius or down to near absolute zero (-270 degrees Celsius) are not unusual. These conditions require specialized plating, materials, and manufacturing processes. Connector manufacturers are developing innovative designs for the medical field, as well as adapting existing connector designs originally specified for the military/aerospace market to suit the health care arena.

Plating and Materials
In meeting “zero defect” criteria for medical applications, connectors are subjected to a number of tests, including shock and vibration, extreme temperature cycling, salt baths, and extended mating cycles. To withstand these conditions and pass each of the tests, connector manufacturers must pay particularly close attention to plating.

While many connector designs incorporate silver plating, silver typically exhibits contact resistance instability when temperatures exceed 85°C. As such, high reliability components often employ a combination of plating materials, such as an underlayer of nickel followed by a layer of gold, which is suitable for operation at temperatures as high as +200°C.

Gold is also suitable for use at extremely low temperatures, and does not lose connectivity due to contact resistance of the material. For example, C&K has received feedback from its customers that its MTB1 Series connector has performed at temperatures as low as minus 270°C. Such temperature extremes can be encountered in high-reliability medical applications, such as cryogenics.

The use of specialized plating materials also allows connector manufacturers to design and manufacture devices to custom specifications, such as a completely terminated connector family, custom designed insulators, shielded and unshielded designs, and the addition of outside molded strain relief to protect contact termination of connector wires.

Beyond plating, high-reliability connectors often require specialized contact systems to enable an extremely secure mating connection. A twist pin contact system, for example, provides a secure base for the contact, and exhibits superior electrical and mechanical characteristics, compared to traditional machined or stamped-contact systems. This type of contact system consists of beryllium copper wire wound around stranded cores. The wire bundle is crimped into a sleeve at one end, while the other end is terminated with a hemispherically shaped weld. The flexible twist-pin is recessed into the insulator and the rigid socket is exposed, reversing the traditional positions of pin and socket. During mating, the socket is guided into the pin insulator by the lead-in chamfer. The pin is kept from flexing beyond the socket capture radius by the walls of the cavity. The hemispherical weld of controlled radius at the tip of the pin combines with the lead-in chamfers of the socket contact and the pin insulator to cam the pin into alignment. The twist-pin contact design provides multiple points of electrical contact, highly reliable crimps, high-current handling capabilities, and extended life cycles. Twist-pin contacts will mate even under severe misalignment.

Special raw materials are also employed in high reliability medical applications. For equipment such as CT scanners, MRI, and ultrasound machines, the use of non-outgassing and non-magnetic metal materials are imperative. Outgassing from certain raw materials used in the connector can negatively affect the performance of the device, producing an inaccurate reading. As a result, a typical requirement of high reliability connectors is to employ materials with no outgassing and low residual magnetism elements, thus resulting in clear images that are not distorted by RF and magnetic interference. These applications often utilize special copper alloy materials that have the additional benefit of wthstanding extremely high temperatures.

Because atmospheric conditions require components used in space applications to include non-outgassing and non-magnetic materials, connector manufacturers are capitalizing on the similar requirements and adapting MIL- and space-qualified connectors for medical imaging equipment.

Manufacturing Processes
Connector manufacturers that have space-qualified manufacturing facilities are easily able to adapt their processes to produce connectors to meet medical specifications. Because no repairs are possible in space applications, zero-defect connectors are specified. The same holds true for medical equipment. With zero-defect manufacturing standards already in place, including ESA, ISO, and EN90001 qualifications and certifications, manufacturers are well equipped to adapt connectors originally intended for aerospace applications to medical equipment.

To achieve the zero-defect specifications, connector manufacturers take special consideration in managing all of the raw materials and component parts that will go into assembling each connector. They ensure that each part is within the defined acceptance limits of the particular application for which it will be implemented.

Before the assembly process begins, all piece parts are inspected at magnification levels from 20x up to 50x, further ensuring no defects are present. High reliability connectors are also subjected to salt baths to ensure there is no infiltration of particles that could cause materials on the connector to corrode.

During manufacturing, all parts are traced as they are received from suppliers, enabling connector manufacturers to find and track the root cause of any potential problems. Finally, at the end of the assembly process, all parts are tested individually based on contact resistance, insulation resistance, and impedance, to name a few specifications, thus verifying that they are in accordance with each specification as requested by the end customer.

By working with a fully integrated connector manufacturer—one that designs, develops and manufactures in the same location as the engineering team—customers are further ensured that all specifications, from concept through production, are met. This in turn allows for the development of custom designs—such as the addition of flat cable, active or passive components, and special brackets for mounting, along with dedicated harnesses. When applicable, existing components with high-grade plating and materials can also be used to meet any medical imaging equipment needs. By working closely together, these teams make it possible to create dependable and powerful medical equipment that will advance knowledge, perfect treatments, and inspire cures.

Gilles Parguey is C&K’s product manager for high-reliability connectors. Parquey has been with C&K for 21 years and has extensive experience in mil/aero products. He is located in Dole, France. For more information, email gilles.parguey@coactive-tech.com or visit www.ck-components.com.