A cochlear implant manufacturere approached Intelliconnect with a request for a rugged, reliable quick disconnect waterproof connector suitable for use in a medical system application.

A cochlear implant, or bionic ear, is a surgically implanted device that enables a severely deaf person to hear again.

The external transmitter (where the connector is required) transmits radio frequency (RF) signals through to the implant via a magnetic connection to reduce the risk of infection. The transmitter processes the RF signals from the microphones through a speech processor and then into the internal implant which connects to the cochlear allowing the person to “hear” the sound.

All the Intelliconnect components are in the external transmitting/processing part of the device so need to be extremely rugged and reliable.

The number of people with implants fitted is estimated to be close to 200,000.

In this case, the customer had a requirement for the connector to be waterproof as the connectors were used close to the skin, and had to be able to be used in normal domestic environments such as swimming pools, showers, baths, high humidity environments such as saunas and steam rooms. The design had to be small enough to fit into the transmitter equipment, but still rugged enough to allow a push/pull connection style be incorporated.

The brief required a new design of connector to be initiated, as two important features – waterproof integrity and a push pull connection, rather than a coupling nut – were required to allow ease of use and performance under severe environmental conditions.

The design was based around a modified MCX connector, with the waterproofing rating of IP68 in the unmated condition. This is the equivalent of 10m immersion in water, tested for a minimum period of four hours. (In fact the connector has been tested to way beyond this level, 60m without leaking thus ensuring a safety factor of six).   

The application requires several thousand disconnects during the product lifecycle, and this meant a development programme needed to be undertaken to ensure the latching mechanism, spring forces and engagement and separation forces be consistent and qualified for the specified number of mating and unmating cycles. This was finally tested to 3000 cycles, and the performance of the connector verified to be within the specified limit after the full life cycle testing.

Other requirements that were subjected to a full qualification test programmes were a wide ranging temperature envelope, giving sufficient safety margins for any eventuality. The temperature envelope is defined from -65 to +165 degree C to ensure full operation with a significant safety margin (to increase reliability) over a wide operating temperature range.

The operating frequency range of DC to 6.0GHz enables all transmitted signals to be fully processed without any subsequent signal degradation.

Insulation resistance of 5.0MOhm allows for any moisture or humidity to be present without compromising safety or performance of the device.

The voltage rating 335v RMS gives a large engineering safety factor within the connector design so that any fault condition can be safely dealt with. 

Voltage standing wave ration (VSWR) of 1.3 allows for the signals to be processed without any degradation or deterioration and produces the best possible signal clarity, explains Intelliconnect.

To allow the external components to be regularly serviced the connector needed to be capable of up to 3000 mating cycles, and this was achieved by fine tuning the connector forces to an engagement force of 2.5lbs maximum and 1.5lbs minimum, and a disengagement force of 3.0 lbs maximum and  2.0lbs minimum.

http://www.intelliconnect.co.uk


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