Connector Design Considerations for the Demanding Medical Market

Challenging environmental conditions and high reliability requirements create the need for can’t fail connectors.   This article explores some of the more critical design factors that go into designing a new connector for the medical market.

The medical industry requires connectors to reliably operate in a variety of harsh environments.  This drives the connector design to be custom, specifically addressing each application’s unique challenges.  There are many attributes that must be considered when laying out a connector’s specifications, but they typically fall into 1 of 3 categories: material selection, mechanical properties and electrical specifications.   All 3 categories must be considered concurrently to yield a successful connector design.

Material selection

Proper material selection will be determined by the environmental conditions the connector must operate in and is often driven by regulatory acceptance requirements.  These factors must be considered from project inception and throughout the entire development process.   Factors can range from flame rated plastics (UL, Vx rated) to chemical resistance.  Chemical sensitive applications may require plating structures that resist harsh chemicals and balance contact life on both sides of the connection system with the electrical requirements.  Base metal selection can also affect connector reliability.  Compliant contact designs with a capability to self-clean by implementing a scrubbing action can also influence material selection.  The development process must also consider materials that are favorable for prototyping, and that can later be scaled into molded form factors when the project reaches high volume production.  Using the proper materials in the prototyping phase can allow design validation prior to the expense of fixed tools, reducing technical risks, and the commercial risks from a delayed program.

A healthcare application with a portable device dock provides an example where all the considerations will play a role.  The stability of the insulator and reliability of the contacts in such a device can be stressed by common field processes such as using beach wipes to clean, or real-world threats like a spilled beverage.   Planning, design and validation provide the best path to avoid a failure or costly pattern of failures.

Mechanical properties

Choosing the contact element type is probably the single most important decision for any connector design.  Spring probes, also known as or Pogo® pins, have proven to be the most reliable means of making contact when thousands of cycles are needed.   The compliance aspect of spring probes also compensates for non-planarity challenges between the contact surfaces as well as blind mate applications.  For portable, wearable or base charging applications, the challenge can simply be maintaining continuity in a dynamic environment.  Shock and vibration tolerant connectors are necessary for rugged environments.   Spring probes are offered in a variety of spring forces and tip geometries, tailored to the application.

Probe architecture is critical when designing the optimum solution.  Probes with a deliberate bias offer the most stable design to transmit power and data.  The mechanics of how to achieve the bias affect; contact resistance, cycle life, signal stability as well as cost are essential elements to a successful probe design.  The available space and required usable stroke of a probe will also dictate internal probe design.

Electrical specifications

The number of signal contact points and layout pattern is typically the first design parameter to consider.  If the signals operate at high frequencies (>500MHz), then multiple ground pins may be needed to ensure proper signal integrity through the connector. With the advent of increasing data streams, and more capable transmission standards like USB2.0, it is more important than ever to understand the influence of an electrical contact.  A qualified solutions provider must be able provide design, simulation, and then validate data transmission through extensive testing.  Many of today’s medical connectors operate at high voltages and high currents.     Contacts must be designed to the electrical specifications needed to achieve the products functions such as cut and cauterize, or micro fluidic control.

In summary, when designing a connector for medical applications it is important to equally consider the materials, mechanical properties and electrical characteristics of the design to ensure a successful product.

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