Medical Electronics
A guide to specifying medical connectors
David Phillips of circular connector specialist binder, discusses key criteria for selecting connectors for medical applications
M
edical devices based on electronics technology can cover everything from disposable, one-time use devices, through hand-held
diagnostics and bed-side patient monitoring to large CT and MRI scanning systems. While specifying electronic connectors for these medical applications requires the same consideration as for many other applications, there are some factors that are unique to the medical market.
There are some basic choices to be made concerning the electrical and physical attributes that are both directly related and fundamental to connector choice. The current, voltage and the number of contacts, together with the cable diameter and level of shielding required all have a direct influence on the connector choice as do the physical characteristics relating to how the connector will be terminated, the method of mating and the space available both inside and outside the product.
The current carrying capacity of a connector denotes the current that can be carried continuously and simultaneously through all of its contacts and is determined by IEC 60512-5-2. The current carrying capacity is not fixed and decreases with increasing ambient temperatures. Certain applications such as MRI equipment call for shielding against electromagnetic interference (EMI) and these necessitate screened cable systems that require connectors with good shielding characteristics and this can be offered with metal bodied or metalized plastic connectors.
Locking systems and ingress protection
How often the connector will be mated and the IP protection requirements have a major influence on the type of mating system and the chosen method will necessarily have a big impact on connector cost. The IP rating determines the degree of protection to dust and liquid. Typically, medical connectors are rated IP54 and above, with many being IP67 for temporary immersion in liquid. Screw connectors provide the ultimate protection against accidental un-mating and have excellent IP performance but, on the downside, they are generally the most expensive type of connector, especially in metal versions.
Push-pull connectors can be
Electrical requirements The connector’s rated voltage and impulse voltage are defined according to IEC60664-1 - a basic safety standard to achieve insulation coordination - specifying clearances, creepage distances and solid insulation, taking into account the voltage stress and surge together with the expected degree of pollution. These factors determine the physical dimensions of the connector.
12 May 2021
expensive. However, the trend towards plastic versions has helped to reduce cost and provides a quick mating IP67 connector with some protection against accidental un-mating. Snap-in and bayonet connectors provide quick and simple mating and are generally the lowest cost solution. Recent developments mean that these can now be rated up to IP67 thus providing an economic solution with high performance.
Components in Electronics
New mating systems such as binder’s just announced innovative Easy Locking Connector (ELC) provide positive mating and protection against accidental un-mating with a unique intuitive locking system featuring snap hooks. Here, the friction free connection allows for over 5000 mating cycles.
The new binder ELC series 570 connector features a PA66 plastic housing, has 12 gold plated contacts for 0.25mm² wires and is rated at 2A, 150V.
The female panel mount connector provides protection against the ingress of liquids, water splash and accidental electrical contact and, when mated, the new easy locking connector offers protection to IP54.
Sterilisation and cytotoxicity As said earlier, medical applications are wide ranging with surgical applications requiring connectors resistant to medical sterilisation via steam autoclave, gamma radiation and gas plasma etc. However, some applications require no sterilisation while others require the use of the type of material we use which have been tested for Cytotoxicity (toxicity to skin) and are free of DEHP phthalates.
Standards
There are a number of standards which should be considered when specifying connectors and EN 60601 is a family of standards whose scope covers the safety, essential performance and electromagnetic compatibility of Medical
Electrical Equipment and Systems. It is technically equivalent to the international standard IEC 60601 and covers aspects such as vibration, shock, rough handling and finger-proofing.
ISO 13485 specifies requirements for a quality management system where an organisation needs to demonstrate its ability to provide medical devices and related services that consistently meet customer and applicable regulatory requirements.
The US Food & Drug Administration (FDA) continues to promote the development of connectors that reduce the risk of device misconnections. These standards promote patient safety by assuring connectors for unrelated systems are incompatible, so the devices cannot be accidentally linked or forced to fit.
Made to measure
Some applications require a hybrid connector to carry a gas in addition to power and signal and in such cases the best solution may be a bespoke connector. This not only provides the optimum solution but also gives the customer protection of its own intellectual property. Naturally, medical connectors tend be expensive – but what price patient safety? binder offers technical and commercial assistance when it comes to specifying the right connector for medical applications.
www.binder-connector.co.uk www.cieonline.co.uk
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