How Small Can Connectors Go?

Miniature, micro miniature, ultra miniature: Bob Stanton explores the trend for ever-smaller connectors

Application-specific connectors and size reduction have come on rapidly. Circuit chip technology has driven us all to new heights in performance, capability and demand. The evolving circuit chips demand much lower voltages and current flow, but are also running faster, store and process significantly more data and provide long battery life. Connector size and size reduction needs are often based on a few key application factors and performance constraints.

Electrical current load is a key consideration. Each connector contact must offer low resistance interface with its mate and carry enough electrical current to satisfy the circuit it is serving. Often, the current limits are going to be set by the diameter of the wire in the cable because wire length times resistance will set the performance and thermal capabilities of the interconnection system.

Signal integrity is also significant. As connectors and circuit modules squeeze into tighter spaces, circuits must still function independently of adjacent circuits. Designs must include protection against signal cross-talk and often times, protect from electro-magnetic emissions and or reception of other signal noise in and about the system.

Environmental conditions must be considered too. Ruggedised connector design for performance in extreme environments is often controlled by specifications assuring continuous signal flow during high shock and vibration and performance during extreme heat and cold cycles.

IP standards are often specified to meet international standards in moisture conditions. Elastomeric seal rings are often built into the connectors to assure moisture does not penetrate the connector and enter into the circuitry. Smaller and smaller seals will be needed as this industry continues to miniaturise.  

Circuit Mobility

Fitting interconnects into robotic hands, squeezing them into probe tips, adding cable to small weather satellites, and mounting cameras on soldier helmets are examples of the drive to squeeze more and more into portable electronics.

Standard designs are reviewed for potential fit and function and they are tailored using solid model designs to meet both the size and the reliability functions. Pin and socket sizes are reduced to minimum sizes that meet the above criteria and still squeeze into the space allowed. Flat leads are used and can be reduced even further when some of the performance and rugged reliability requirements are reduced.  

The Challenge And The Market

Careful use of shape and spacing has allowed another level of high-density interconnection. Use of unique low dielectric strength insulator materials also allows size reduction as circuit speed increases and size decreases. Price and ruggedness continue to play a key role in how small we can design our connectors. This future of the more ruggedised technology is on the move and we have yet to see how small we will go. We are currently seeing larger connectors such as the Circular 38999 being replaced by smaller and lighter micro-circular connectors that use .050in pitch. Increasingly, we see nano-circular connectors at .025in pitch handling multiple high-speed signals well.