The serviceable points of connectors should have proper detachment mechanism. Some connectors are pluggable while others are directly soldered to the board. Using pin headers, wherever possible in the design, ensures ease of servicing.
Speed, capacity and other factors. Another criterion for selection of connectors is based on the kind of performance they can handle in terms of speed and response time. Choose connectors based on the standard ratings of voltage/current capacities and wire gauges they offer.
Determining the peak capacity is important as, if the device reaches peak consumption or has a current burst, it may no longer work reliably. The connector manufacturers typically define the specifications very clearly in their datasheet. If the tolerances are within the range of the particular component, the user will not have performance issues.
Grounding and shielding are necessary requirements for EMI/EMC, RF, grounding, power and signal separation and many data-critical applications. Having snap-fit or locking sockets is another critical need for continuously or frequently moving devices. We now have double lock and triple lock facilities for connectors. The security standpoint can also be a factor—whether or not anybody can easily bypass into the communicated signal.
Standards to be fulfilled. Having appropriately certified cables and connectors (such as CE, UL and ISI) is a mandatory requirement for professional designs. Regulatory requirement such as Restriction of Hazardous Substances (RoHS) directive also needs to be fulfilled. In certain specific fields of application, like in the case of military uses, connectors used may require a specification such as MIL grade.
USB, HDMI, D-subminiature and/or DIN are the standards to be complied by I/O connectors for serial communication, modular jacks, audio jacks and RCA connectors.
Zero insertion force (ZIF) connectors can be used as on-board connectors for display modules or cameras, rectangular shrouded/unshrouded connectors, external cables and for testing and programming purposes.
Additionally, in some embedded systems for special applications, high-speed back-plane connectors, microprocessor and memory chips sockets and standard memory or SIM card connectors would also be required.
Though very rarely seen, sometimes there also exist a set of geo-specific standards defined by countries or regulations. They insist on using a specific type of connectors for specific applications.
The author is a dancer, karaoke aficionado, and a technical correspondent at EFY. Find her on Twitter @AnuBomb.