Staying Connected - December 2008

Smaller Connectors to Match Shrinking Electronics

As medical electronic devices shrink in size we are regularly asked to provide smaller and smaller connectors.  Most often we are being asked for a flat or rectangular connector to meet the low profile design of the device.  While designing and manufacturing small connectors is not difficult, designing small connectors that meet requirements unique to medical applications can be very challenging.

Size Matters

Small connectors can be
difficult to handle for some users

Electronics are shrinking to a point that devices can be too small for some users to comfortably handle them.  As an example, the new iPod Nano is a remarkable engineering achievement.  The 1.3 ounce device holds thousands of songs, plays videos and displays photos.  Because the Nano is so compact, controls and connectors are also very small.  Often the elderly or infirm with less than optimum dexterity and vision find it difficult to handle such small devices.

Medical devices, including cable assemblies and connectors, should be large enough to be comfortably and effectively used by any potential operator.  When devices are used in a clinical setting connecting the cable should be intuitive and easy even under stressful emergency conditions.  Size and usability become even more important when devices are used outside of a clinical environment.  Connectors should be large enough for untrained, elderly, or users with health problems to easily use.  Any markings on the connector or device should be large enough for users with poor eyesight to see easily.

Electrical Characteristics

Electrical safety is addressed in various domestic and international regulatory standards.  These requirements place additional requirements on cable assemblies, wires and connectors used with medical devices.  Requirements for dielectric and defibrillation withstand requires medical cables and wires to be more robust than for most digital electronic applications.

The need to withstand defibrillation current in wires and cables can be reduced by placing appropriate protective resistors at or near the patient termination point; often in the molded electrode snap, pinch, or banana plug assembly.

We are often asked why medical cables can’t be as small as cables used with consumer electronic devices.  Wire and cable designed for digital electronic applications do not need to handle as high of voltage as medical applications.  Conductors can be a much smaller gauge and the amount of insulation can be reduced allowing much smaller diameter cables.

To achieve dielectric withstand requirements of AAMI EC53, adequate insulation between the conductors, shields and other conductive components is required.  The need for larger conductors and adequate insulation increases the size and decreases the flexibility of wires and cables used for medical applications.

Low Noise Considerations

Most medical applications require or benefit from wire and cables that produce very low amounts of triboelectric noise.  Triboelectric noise is generated within wire and cable when the material is flexed and components rub against each other.  Affinity has engineered a variety of cables and wires with triboelectric noise far below the AAMI EC53 requirement of 50 micro-volts maximum.  To achieve excellent low noise characteristics wire and cable diameter is required to be somewhat larger than if noise were not an issue.  The somewhat larger diameter cable and wire often mean that the size of the connector needs to increase.

Size Constraints of Small Off-the-Shelf Connectors

Many small connectors are available as off-the-shelf items.  However, the vast majority of these are designed for non-medical applications.  Some would be the perfect size for small ECG devices except for the fact that the contacts are typically so close together that they will likely fail EC53 dielectric withstand test of 1,000 volts and will not survive defibrillation pulses.

Besides not meeting several biomedical electrical standards, connector contacts are often spaced too closely for shielded conductors to be terminated side by side.  Shielded medical grade wire with 28 gauge conductors typically has an outside diameter of approximately .090” (2.25mm).  To terminate this size wire requires minimum contact spacing of at least .100” (2.5mm) in each axis.

Example of compact 10-position
connector which will not accept
wire with a diameter greater
than .060” (1.5mm)

Back shell opening of .210” (5.4mm)
will only accommodate 4 strands of
.090” (2.25mm) shielded leadwires

In addition, many small off-the-shelf connectors come with shells that are assembled over the connector body.  The pre-formed strain relief or back-shell is often not large enough to accommodate either a larger diameter multi-conductor cable or required number of individual lead wires.

Mechanical Strength

The signals transmitted by most medical devices could be carried by very light gauge wire.  However smaller gauge wires have less tensile strength than larger gauge wires.  Wire gauge is less important in multi-conductor cables, but becomes significant as it relates to individual leadwires.

Small diameter wire is typically
not strong enough to withstand
repeated pulling to disconnect
snap from electrode patch

Leadwires typically are terminated on the patient end to an electrode snap, pinch connector or banana plug.  While not recommended, it is probably most common that various connectors are removed from the electrode by pulling on the leadwire.  If the wire itself or the termination is not strong enough, the wire may break or separate from the connector assembly.  Experience has shown us that using either copper conductors 28 gauge or larger or tinsel conductors with a Kevlar core will provide enough strength to withstand repeated removal from electrode terminations without failure.

Small Connector Options

Several options are available if a small connector is desired.  The most obvious is to find a small off-the-shelf connector that meets the electrical, mechanical and size requirements.  Occasionally, components of an off-the-shelf connector can be used with modification.  Modifications can include overmolding the connector or producing new top and bottom shells to capture the wire or cable being used.

Example of a small custom
connector designed for
ambulatory monitoring

Size and cost are reduced by
designing connector to plug
directly into PCB eliminating
mating connector

For the greatest design flexibility, a custom connector may be desired or required.  Benefits of a custom connector can include a large degree of freedom in choosing number of contacts, size and shape, and incorporation of logos and custom markings.  An additional benefit of a custom connector is to prevent accidental connection by incompatible devices.

One option we have used to both reduce size and cost is to design the cable connector to plug directly into the PCB in the device.  This method not only eliminates a separate mating connector within the device, but can be designed to either make it easy or difficult to replace the cable.


If you are looking for a compact method to connect to your device, consider working with the Affinity engineering team.  Once we understand your requirements, we can assist you in selecting the best option whether it is an off-the-shelf or custom connector as part of a new cable assembly.

At Affinity we judge our success by our customer’s success.  By using our well- defined design and development process and communicating regularly with our customers, we keep our projects on schedule and ensure that what we produce meets or exceeds our customer’s expectations.

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Meet Sal Godinez – Affinity Shipping, Receiving and More

Sal Godinez

At Affinity Medical Technologies, if you absolutely, positively have to get a shipment sent to a customer the person who will take care of it is Sal Godinez.

Sal joined the Affinity team in Shipping and Receiving a little over two years ago.  After graduating from high school, Sal managed a sandwich shop for five years before joining Affinity.  His enthusiasm, helpful attitude and friendly personality are appreciated by everyone at Affinity Medical.  

Most of Sal’s day is spent in the Affinity warehouse where he manages raw material and component inventory, receives deliveries and prepares shipments for both domestic and international customers. Sal works closely with freight forwarders to scheduling pickups and provides the necessary paperwork and export documents.

Sal is versatile and has been trained to help in production if needed.  Sal also assists the office and engineering staff by stocking office supplies, sending samples to customer and hand delivering couriered packages. 

Sal’s primary duties at Affinity
are receiving, shipping,
and inventory control

Sal assists Kevin Kom, Affinity’s Production Manager, with maintenance and minor repairs.  He also handles room set up for employee meetings and company events. Sal has proven to be a very versatile team member.

Sal recently completed Lean Manufacturing training at Affinity and is working to incorporate Lean principles in his everyday work activities.  When asked why he likes working at Affinity Medical Technologies, Sal said, “I appreciate the opportunity to learn new skills with on the job training. In this way, I can increase my responsibilities and contribute more to the company.”

Sal is trained to assist in
production and also helps with
repair and maintenance

Sal attends college part-time.  He previously studied Business Management but is now studying Mechanical Engineering.  He looks forward to earning his undergraduate degree in the near future.

Sal, who’s Mother also works at Affinity Medical, lives in Orange County with his family. In his free time, he enjoys participating in sports and watching his favorite soccer team, Manchester United.  Sal is also a big fan of college football and attends USC home games with his girlfriend who has season tickets.  He also enjoys weekend trips with friends to interesting spots in California and beyond.

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Affinity Secrets Revealed for Holidays

Quality starts with our
dedicated team of Elves

As we rech the end of 2008, and in the spirit of the season, we thought we would share again one of the secrets of why Affinity cable assemblies are so good.  They’re built by elves!

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Announcements and Information



Affinity Medical Technologies will be closed Wednesday, December 24th through Friday, December 26th.  We will reopen on Monday, December 29th.

For New Years, we will be closed only on Thursday the 1st of January and have limited staffing on Friday the 2nd.

From all of us at Affinity Medical, “May your Holidays be Merry!”

Suzann Sitka and Candy Golding
- Affinity Customer Care Team

Affinity Customer Care - Hours of Operation

Affinity Medical Technologies customer care specialists are available from 7:00 A.M. until 4:00 P.M. Pacific Time.

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Affinity Medical Technologies

1732 Reynolds Ave
Irvine, CA 92614  USA
Phone: +1 949 477 9495
Fax: +1 949 477 9499