Bench Talk

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Electronic equipment is communicating faster than ever before. With data speeds exceeding 100 gigabits per second (Gbps), satisfying the competing requirements for performance and miniaturization is forcing connector manufacturers to develop new technologies. Printed circuit boards and the connectors that link them are the core of this communication, providing the pathway for sharing the required data.

The industrial world has an enormous appetite for data. In areas such as manufacturing and automotive design, the rise of edge computing is also creating a new range of challenges for board-to-board connectors. Edge computing and its latest development, edge artificial intelligence (AI), place equipment in the field, close to the source of data, where the shorter distance between the source and destination reduces latency.

This minimal latency is vital in applications that need to act in real time, such as autonomous vehicles and safety-critical systems. As a result, sophisticated electronic systems are being deployed into the harsh conditions of factory floors, freeways, and smart cities. While board-to-board connectors may be protected inside hardened enclosures, they are not immune from damage caused by shock and vibration, and designers need to understand the impact of these conditions while delivering secure communication.

The need for high-speed connectors is not limited to the industrial world. Advanced consumer devices, such as virtual reality glasses, the latest smartwatches, and wearable electronics, drive innovations in miniaturized design. To keep pace, connectors are getting smaller, and the latest generation of board-to-board connectors features pitches of 0.5mm or less. With such low-profile applications becoming common, manufacturers and designers must achieve the smallest possible connector packages while still delivering realistic performance.

Making Smaller Connections

Designers of fine-pitch connectors face many challenges. The first challenge is physical robustness. In a connector with a pitch of 0.5mm, the contacts must be even smaller to allow enough space between each contact and the next. Small contacts like these are vulnerable to damage and therefore require special handling.

A connector also requires an insulator body, which keeps contacts separate. This insulator body also delivers mechanical protection, preventing damage during use. Connector insulators are molded parts that are made from one of several types of dielectric materials. These materials must be very thin to be useful in fine-pitch connectors. When contacts and connector housings are made from such thin materials, board-to-board connectors face challenges in everyday use as they may be too fragile. This is also a consideration during the manufacturing process itself. Connectors must be capable of mass production. In the race to create ever-smaller connectors, manufacturers must be aware of the fragility of their designs.

This fragility is essential, as board-to-board connectors perform both mechanical and electrical functions. Providing the physical link between two PCBs, whether parallel or perpendicular, connectors must be designed to withstand mechanical force. As data speeds increase and processor power consumption grows, connectors perform a role in thermal management as well, ensuring that PCBs are fixed at the appropriate distance and orientation to allow airflow for cooling.

Fine Pitch and High Speed

Designers must also consider the intended use of these connectors. A connector with a 0.5mm pitch requires equally compact traces on the PCB, necessitating meticulous PCB layout design. When populating the PCB with components, connectors must be positioned with high precision. For 0.5mm pitch connectors, the placement tolerances are even tighter. Precise placement is crucial, especially when the connectors are used to link two parallel boards.

The fine pitch of PCB traces and PCB contacts also impacts the electrical signals that they carry. With parallel traces so close together, there is the danger of crosstalk—the interference of one signal trace caused by another. As higher-speed communications become common, signal integrity (SI) takes on even more importance.

SI describes the quality of the electrical signals transmitted over a cable and through connectors. Many internal and external factors influence SI. Engineers must understand the electromagnetic interference (EMI) created by the external environment and how it affects the quality of the signals that are carried through a connector system.

High-speed signals transmitted through cables, connectors, and PCB traces can interfere with each other. The closer these channels are, the more they can impact each other, and this tendency grows with higher transmission speeds. The growing importance of SI has highlighted the importance of the break-out region (BOR), the section of the board where signals leave the connector itself and transition onto the PCB.

However successful a manufacturer has been in designing a connector to maintain SI, this work can be undone by a poor BOR layout. As a result, many manufacturers provide customers with optimized templates to create a clean interface at the edge of the BOR.

Conclusion

The demand for high-performance communications means connector manufacturers must constantly develop new solutions. However, customers should remember that speed is just one requirement of board-to-board connectors. Robust design, easy assembly, and the challenges of thermal management all need to be addressed to get the best performance from the latest high-speed systems.