Multipin Connectors Offer a Flexible Layout in Support of High Signal Integrity

We are well aware that data rates increase with each iteration of electronic system architectures, with faster clock and multibit-per-clock modulation techniques operating next to power buses in ever higher densities. Managing circuit interconnections in this environment requires us to work hard to maintain signal integrity, minimize transmission losses, reduce susceptibility to noise, reflections, and crosstalk, and meet the bit-error-rate (BER) requirements of modern data buses.

A critical area of concern for many is multipin connectors, which are the focus of signal-integrity improvements. High pin counts that combine differential, single-ended, and power signals require careful layout and considerable flexibility. Additionally, the connector contacts need to be designed to ensure compatibility with high data rates and long contact life.

Samtec, a manufacturer of a broad line of electronic interconnect solutions, has expanded its high-density AcceleRate HD array connector (Figure 1) product range to help address these many challenges.

Figure 1: Shown is a male/female pair of AcceleRate HD open-pin-field array connectors designed for high-speed and high-cycle applications. (Image source: Samtec)

This family of connectors is ultra-dense, multi-row, and features a compact pitch of only 0.635 millimeters (mm) (0.025 inches (in.)) and a width of 5 mm (0.197 in.). It uses an open-pin-field design for maximum layout flexibility, while the connectors’ Edge Rate contacts provide high signal integrity with low insertion loss for bus speeds of 64 to 112 gigabits per second (Gbits/s) and high-cycle connector life.

The AcceleRate HD arrays are available with contact counts ranging from 10 to 100, in increments of 10 per row. With up to four rows, the total contact count ranges from 40 to 400.

An example of a mating set of 400 position arrays is the ADM6-100-08.5-L-4-0-A-TR male connector and the ADF6-100-07.5-L-4-0-A-TR female connector. These connectors are intended for surface mounting on printed circuit boards (pc boards). Mezzanine applications, where a daughter board is mated above the pc board, are accommodated with lead styles supporting mated heights of 5, 7, 9, 10, 11, 12, 14, and 16 mm (0.197, 0.276, 0.354, 0.394, 0.433, 0.472, 0.551, 0.630 in.) to match the required clearances.

The benefits of an open-pin field

The capabilities of a connector’s contacts are only partially determined by their design. The physical arrangement of the contacts, as well as their positions relative to other contacts, are contributing factors. An example of this type of interaction is the use of large cross-section pins intended to carry power; high currents require larger diameters, which reduces spacing between contacts and limits the maximum voltage that can be used. An alternative is to use an open-pin field, where each pin position is available and has no predefined function (Figure 2). The open-pin-field design provides maximum grounding and routing flexibility by allowing the use of differential pairs, single-ended signals, and power through the same interconnect.

Figure 2: The pin positions in an open-pin-field connector are all independent and can be assigned as needed during the design process. (Image source: Samtec)

Pin assignments can vary; differential signals may use adjacent pins for paired connections, leaving intermediate pins open to provide isolation between conductors, as shown in green. Single-ended wires can be assigned to separate pins, with or without intermediate isolation pins, as shown in blue. Power connections that require a larger conductor diameter can be created by connecting multiple pins in parallel, as shown in red.

Edge Rate contact design

The Samtec AcceleRate HD connectors, including the ADM6-100-08.5-L-4-0-A-TR and the ADF6-100-07.5-L-4-0-A-TR, not only offer high signal density and mechanical flexibility, but also feature enhanced signal integrity that supports data rates up to 64 Gbit/s PAM4 (PCIe® 6.0/CXL® 3.2) signaling. PAM4 is a challenging signal because it uses four voltage levels instead of the two used in older non-return-to-zero (NRZ) signaling. This reduces the signal amplitude changes by a third, making the signal-to-noise ratio (SNR) a significant concern.

Samtec addresses this challenge by delivering high signal integrity through its advanced Edge Rate contact system (Figure 3). This system features milled contact surfaces, resulting in smooth mating, reduced wear, and increased toughness for high-cycle applications.

Figure 3 : The mating surfaces of Edge Rate contact pins are milled to reduce wear and ensure low-resistance connections. (Image source: Samtec, annotated by author)

The AcceleRate HD connectors are available with gold-over-nickel plating on a copper base. The Edge Rate contact geometry is designed to match 50 and 100 ohm (Ω) interconnections. Broadside coupling and crosstalk are minimized by aligning the thin cut edges of the contacts to face each other.

Conclusion

As we work to meet the challenges of power and high-speed signaling in compact form factors, Samtec’s AcceleRate HD connectors offer robust support. They are designed and manufactured to handle hundreds of I/O in a compact footprint without sacrificing signal integrity.