Explore interconnect innovations that save space
Small is beautiful for the designers of many consumer, industrial, medical and automotive devices. Smaller is easier to carry, wear or locate in the home or office. Small devices are simpler to deploy in large numbers and have a lighter payload for machines or vehicles.
When it comes to selling style and practicality, smaller is often better. At the design stage, engineering teams are under pressure to reduce the size of enclosures and PCBs. All end-markets want more functionality in a reduced form factor.
Moving power and signals in, out and between different boards or components such as keyboards and displays demands space-efficient connectivity. Connector makers are constantly innovating to meet these demands.
Smaller connectors save space on the PCB. This is an advantage for wireless device designers, as they can optimize antenna design and placement for performance and bandwidth. Most PCB-mounted antennas come with design guidelines. The keep-out area around a board-mounted antenna makes positioning the ground plane and RF signal traces critical. If these design guidelines cannot be met, a different type of antenna may be needed. The extra evaluation and design work could delay the project.
Using a printed antenna placed against the inside of the enclosure may call for a different housing material better suited to RF performance. If a custom antenna is necessary, this could be time-consuming and expensive.
Making connectors smaller without impairing electrical or mechanical performance requires careful attention to the materials used and the design of mechanisms for cable insertion, mating and locking. Simply making molded structures smaller may increase vulnerability to deforming or breaking. The lifetime, measured in mating and un-mating cycles, may be reduced. The current rating per contact, as well as thermal performance and maximum operating temperature, may be lower. Careful design can deliver miniaturization without compromising reliability or robustness.
Signal density up, device sizes down
Electromechanical interconnect suppliers face demand for smaller formats but with higher pin densities. Signal integrity and power are significant challenges in the drive toward smaller connectors.
Connectors shrink from mini to micro
Connectors with a finer pitch permit more contacts in a smaller space. Some manufacturers offer proven and popular connector families in a variety of sizes. Wire-to-board connectors are available in standard, mini and micro versions with a contact pitch of 2mm, 1.5mm and 1.2mm respectively.
Designers also have access to wire-to-board power connectors in various sizes for space-constrained applications. As an example, top-entry, side-feed connectors are aimed at power supply applications in small equipment.
The top entry contrasts with typical horizontal-mating power connectors that require a clear PCB area in front of the receptacle to allow the plug to be inserted. Small components such as surface-mount device (SMD) chip passives can be placed in front of the top-entry connector. Also, the receptacle can be seen from above and helps the operator align the plug accurately for insertion.
One version with a 1.7mm contact pitch and 1.8mm mated height has a current rating of up to 5A per pin, and a lock capable of withstanding 5N of upward cable pull force. A smaller, 1.2mm-pitch version has a swing-lock mechanism that results in a lower mated height of 1.4mm and a typical current rating of 1.5A. A 2-contact configuration is available that puts the contacts on a 2.4mm pitch allowing up to 3A per pin and an increased voltage rating of 100V.
Hybrid connectors combine power and signal
A popular way to save space is to use flexible printed circuits (FPC) and connectors that carry power alongside signals. Some hybrid connectors featuring a contact pitch of 0.35mm can support 10Gbps signals and carry up to 5A.
One of the smallest variants available has six signal contacts in a body just 3.65mm wide and 1.7mm deep. The mated height is also shallow at 0.6mm. Guides aid accurate self-alignment, despite the connectors’ small dimensions. A metal cover prevents damage or disconnection.
Connections come in many forms
End-products of any size and all applications require a wide diversity of connectivity, both internal and external. Some may remain connected after assembly; others may be frequently disconnected. Appreciation of these factors helps during selection.
Ensuring reliability in shrinking interconnect
Surface-mounted compression connectors can provide a simple and reliable board-to-board connection in a small footprint. The individual contacts press against the corresponding receptacle by spring action, which can reduce dependence on a miniaturized connector mating and locking mechanism and allow small dimensions with high reliability.
These types of connectors are popular in applications where vibration is common. They provide the electrical integrity of a large connector within a small footprint. Various types and configurations are available, including connectors with ten 3A-rated contacts on a pitch of 1.25mm that can be used for power and signal connections.
Connectors with a single contact, often called spring fingers, provide a space-saving and reliable option where a single earth or power contact or a small number of signal contacts are required. The height can range from less than 1mm to several millimeters, allowing flexibility to design for various board spacings without changing the PCB layout. The smallest versions can have a footprint below 2mm2 and feature strong sidewalls to prevent over-compression.
Single-connection PCB sockets are another space-saving option where one or a small number of electrical contacts are required. They allow a low profile, less than 1mm above the board, and bring additional advantages such as simplifying removal and re-insertion of replaceable components such as sensors. They are also ideal for odd-form components that do not fit in a regularly spaced socket strip. Versions are available for top-side and bottom-side insertion, and for pin diameters down to 0.8mm, some types offer three points of contact to maintain a reliable connection in harsh conditions. These sockets can be found in push-fit or solderable variants.
Delivering more power
In applications like cloud computing, particularly involving AI and deep learning, high-performance PCI Express (PCIe®) accelerator cards are adopting graphics processing units to increase compute throughput. While the card form factor and card interconnect are fixed, the power demand has risen beyond the limits of the standard PCIe interconnect.
To meet the increased power demands, the PCIe Card Electromechanical (CEM) 5.0 standard defines 12V auxiliary power connectors, first in 2x3 75-Watt and 2x4 150-Watt configurations. More recently, the PCIe 5.0 standard introduced the 2x6 12VHPWR connector capable of powering cards up to 600W. Featuring power pins made from a high-conductivity copper alloy, the CEM-5 PCIe connectors can deliver up to 9.5A per contact. The 3mm contact pitch, compared to 4.2mm for the 2x3 and 2x4 connectors, permits significantly greater power delivery within a comparable footprint, and the connectors feature fully isolated terminals with positive locking for secure mating.
Conclusion
Responding to demands for handheld, wearable and compact industrial devices, connector manufacturers are offering new connector families that help to save space and support greater functionality and performance.
Ingenious mechanical design features and new materials are among the enabling innovations that permit more signal contacts and greater power capability within similar or smaller form factors.
As a global leader in IP&E solutions, Avnet has a robust supplier line card in all regions as well as extensive design support and demand creation services. Our dedicated IP&E experts can help with everything from supply chain needs to service organization requirements.