Roy Phillips, Managing Director at Intelliconnect explores the advancing medical world, with a cochlear implant quick disconnect connector solution that offers a custom design with life enhancing benefits

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

The external transmitter, where a connector is required, transmits RF signals through to the implant via a magnetic connection to reduce the possibility of patient 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.

After suffering failures of standard connectors a major manufacturer of cochlear implant technology approached connector specialist, Intelliconnect with a request to develop a rugged, reliable quick disconnect waterproof connector that would be suitable for use in such a medical system application.

The proposed connector was to be in the external transmitting/processing part of the device and needed to be extremely rugged and reliable.

Latest estimates of the number of people with implants fitted is close to 200,000 with the reliability of all components expected to be in excess of 99.5 percent.

The custom designed connector had 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 and high humid environments such as saunas, steam rooms etc. The design had to be small enough to fit into the transmitter equipment, but still rugged enough to allow a push/pull connection style to be incorporated.

The brief required a new design of connector to be initiated, as two important features -namely 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.

Connector design requisites

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 level of six).

The application required 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 was completed.

Other requirements that were subjected to a full qualification test programmes included:

A very wide ranging temperature envelope, giving sufficient safety margins for any eventuality- the temperature envelope being defined from -650C to 160C 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 6GHz enables all transmitted signals to be fully processed without any subsequent signal degradation.

Insulation resistance of 5Mohm 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.

VSWR 1.3 allows for the signals to be processed without any degradation or deterioration and produces the best possible signal clarity.

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 3.0lbs maximum and 2.0lbs minimum.

The successful design is now in volume production improving the quality of life of both adults and children and in the case of children in particular allows for normal schooling and participation in the hearing world – all thanks to a miniature waterproof RF connector.