Connectors form an important link in a signal's transmission chain. Therefore, when designing high-speed systems, don't overlook them. With the right parts, proper PCB materials, and proper design, you can meet the demand for high data rates.
Mechanical vs. electrical interconnects
Prior to today’s high speed design requirements, the issues of concern for interconnects were the physical aspects of their designs and factors that influenced those designs. These aspects and factors include:
- Stack height or distance between boards
- Termination types required (through-hole, press-fit, SMT)
- Latches or locks
- Supports/Constraints such as standoffs, brackets, chassis slots or frames
- Processing and operating temperature
- Humidity ranges
- Shock and vibration requirements
- Safety issues and specifications
- Adherence to environmental standards such as RoHS compliance, lead-free standards
- Packaging and auto placement requirements
As system speeds have increased, interconnect design is no longer based solely on mechanical requirements. Designers now have to take into account electrical performance issues such as insertion loss, return loss, crosstalk, skew, and propagation delay, to name a few. As with every aspect of high-speed product development, the successful design of any interconnect involves achieving the right balance between maximising the physical and mechanical strength of the interconnect while optimising SI (signal integrity). Interconnect design and manufacture has to be approached as part of the overall system level design process.
It's all about the footprint
The essence of any interconnect design is the footprint, which is sometimes defined by mechanical considerations and other times by SI considerations. Specifically, the factors that affect SI performance include footprint configuration, size, spacing of the pads, PTH (plated through hole) vias, and BOR (breakout region). A graphic of footprint/routing design is shown in Figure 1. Additional factors to consider include maintaining signal integrity through the space/trace relationship and determining via diameters, tolerance stack-ups, number of