Low-Contact-Resistance Sockets Form the Heart of High-Current Connectors

Applications that require the transfer of high-current, high-voltage electricity through connectors continue to grow. These applications include electric vehicle (EV) charging, whole-house backup batteries, and batteries supporting the smart production and storage of electricity. They are also found in the expanding field of data centers, where power distribution units (PDUs), uninterruptible power supplies (UPSs), routers, and power shelves manage high-current inputs at high voltage. Manufacturing and factory floor systems, robotics, and environmental controls also require these specialized connectors.

Connectors in these applications need to support high-current, high-voltage inputs in ever smaller spaces without unnecessary losses. Efficient power transfer is also important to prevent the voltage drops that lead to overheating, which can damage equipment and start fires. At the same time, these connectors must support fast and automated assembly while being error-proofed to prevent equipment damage and rework.

One high-current, high-voltage technology that works in many different types of connectors is Molex’s COEUR socket technology, which minimizes the contact resistance in high-current applications. Products built around COEUR sockets ensure secure connections, allow more devices to fit in less space, and streamline manufacturing.

The core of high-current, high-voltage connectors

COEUR sockets are cone-shaped in which multiple angled contact beams made of highly conductive gold are arranged in a circle (Figure 1). Diameters range from 3.40 mm to 11.00 mm, and they are paired with silver pins sized for a press fit.

Figure 1: COEUR socket connectors provide low contact resistance for high-current, high-voltage applications with gold contact beams arranged in a conical shape that flares at the top. (Image source: Molex)

The pins touch the contact beams at the cones’ narrowest points, beyond which the beams flare out slightly at the cones’ tips. The angled shape ensures each bar has an elliptical contact area, not just a point contact, with the inserted pin. The larger contact areas lead to less contact resistance, which reduces voltage drops and heat generated from the connectors.

Another advantage of this low-contact-resistance design is the ability to pack electronic components more closely together, saving space. COEUR sockets are all 10.0 mm tall, a height which works in multiple connection scenarios, like wire-to-board, wire-to-bulkhead, board-to-board, and board-to-busbar.

High-voltage, high-current connector characteristics

Connectivity solutions using COEUR socket technology are designed to handle high currents and high voltages. For instance, the Sentrality pin and socket interconnect system can handle 75 A to 350 A at up to 1,000 V with contact resistances between 0.20 mΩ and 0.40 mΩ. These characteristics allow the system (Figure 2) to efficiently connect printed circuit boards (PCBs) to each other or to busbars in home energy storage, industrial automation, networking, and telecommunications applications.

Figure 2: In the Sentrality pin and socket interconnect system, COEUR sockets enable high-current, high-voltage connectivity with PCBs and busbars. The system minimizes board stack heights and ameliorates tolerance stack-up with ±1.00 mm of radial self-alignment. (Image source: Molex)

In SW1 wire-to-board connectors, COEUR sockets with a contact resistance of 0.25 mΩ allow safe transmission of 120 A to 300 A at 1,000 V over wire sizes ranging from 2 to 4/0 AWG (0.258 in. to 0.45 in. diameters). The polybutylene terephthalate (PBT)-shrouded connectors (Figure 3) are common in factory floor, robotics, and home energy storage applications.

Figure 3: SW1 interconnects use COEUR sockets to safely connect high-current, high-voltage cabling with PCBs and busbars. The one-handed positive locking design also eliminates cable bends with a 90° connection. (Image source: Molex)

Finding the right fit with high-voltage, high-current connectors

COEUR socket technology minimizes the space needed to implement high-voltage, high-current connections. Connectors like the Sentrality system keep the stack height between PCBs or busbars small. While one board has the option for press-fit or surface mount technology (SMT), designers can choose a press fit for the other for a 1.50 mm stack height, SMT mounting for a stack height of 1.75 mm, or a screw-mount option for a stack height of 4.5 mm.

The HyperQube cable-to-board or cable-to-busbar connector (Figure 4) also has a small footprint at 12.3 mm by 15.5 mm. It uses COEUR socket technology to handle 120 A with 0.20 mΩ contact resistance over 6 AWG to 2 AWG wires (0.162 in. to 0.258 in. in diameter). HyperQube’s mated dimensions are 19.5 mm by 43.7 mm by 17.7 mm.

Figure 4: HyperQube connectors are a compact way to connect high-current wires or cables to PCBs or busbars. A removable screw-mount design, mechanically keyed locating pegs, and color coding streamline HyperQube installation. (Image source: Molex)

In addition to efficient use of board space, electronics designers worry about accommodating cables’ minimum bend radii. They look for designs that allow cables to connect without bending, for instance, with a 90° design option and 360° rotation during assembly. COEUR-socket-enabled HyperQube and SW1 connectors do this. UltraWize connectors also have a 90° geometry to join wires to PCBs with space-saving staggered locating pins (Figure 5) that can handle 170 A and 125 V with 0.4 mΩ contact resistance.

Figure 5: UltraWize connectors have staggered locating pins to efficiently connect wires carrying up to 170 A at 125 V to boards. They have UL94V-0 flammability resistance, 125 V_AC dielectric withstanding, and 500 V_DC insulation resistance. (Image source: Molex)

Some products, like the Sentrality system and PowerWize Blind-Mate Interface (BMI) interconnects (Figure 6), also permit radial self-alignment, which can help relieve tolerance stack-up. PowerWize BMI panel-to-board and panel-to-busbar connectors manage ±2.00 mm of radial self-alignment, along with built-in guide rails for gross alignment, in applications that handle 75 A to 185 A with 0.10 mΩ to 0.25 mΩ of contact resistance.

Figure 6: PowerWize BMI connectors support blind mating with guide rails and ±2.00 mm self-alignment. Screw-mount and solder-tail options attach them to busbars and PCBs. (Image source: Molex)

Designers of high-current and high-voltage electronic systems also need to streamline assembly. Many COEUR-socket-enabled connectors are supplied in tape or reel form, or in pick-and-place trays for automated assembly. Features like mechanical keying, color coding, and audible clicks eliminate human error during assembly. All COEUR-socket-enabled connectors are rated for a minimum of 200 mate-demate cycles per EIA-364.

Ensuring safety in a high-current, high-voltage environment

For applications that deal with high currents and high voltages, safety is at least as important as space savings and efficient assembly. Touch-safe designs, fire retardance, less toxic materials, and wide operating temperature ranges are some of the ways component designers have made these connectors safer.

Many connectors that use COEUR sockets to allow the efficient flow of high currents are designed to be touch safe, meaning that current-carrying components are shrouded, enclosed, or otherwise protected from direct human contact. Connectors designed to be touch-safe include the HyperQube, PowerWize BMI, and PowerWize wire-to-board crimp connectors and assemblies (Figure 7). PowerWize crimp connectors use an eight-sided crimp geometry to securely attach wires from 10 AWG to 1/0 AWG (0.120 in. to 0.525 in. diameters) to PCBs or busbars. Their screw-mount design includes a touch-safe PBT locking header and receptacle with audible feedback.

Figure 7: PowerWize crimp connector components use an 8-sided crimp profile to keep contact resistance low in 10 to 1/0 AWG wires that handle 120 A to 175 A at 300 V to 600 V. Headers, connector housings, and assemblies are touch-safe PBT. (Image source: Molex)

PBT is common in electronics applications due to its excellent electrical insulation. It is used in UltraWize, PowerWize, HyperQube, and SW1 connectors. These connectors are also rated low-halogen or halogen-free, assuring users that, in the event of a fire, smoke from the components will be less toxic.

PBT also has good fire-retardant properties, even without the use of halogen-based fire retardant. All connectors mentioned above are rated UL 94V-0 fire retardance, meaning any flame will self-extinguish within 10 seconds from the removal of the source of ignition without producing any flaming drips.

Conclusion

COEUR socket technology’s multiple angled contact beams ensure a low contact resistance to enable high current transfer with minimal voltage drops or heat generation. With these properties, COEUR sockets form the heart of multiple connector types designed to carry high-current, high-voltage electricity.

Connectors using COEUR sockets are also designed for space efficiency and ease of assembly on PCBs, busbars, panels, and bulkheads. Fire-retardant and touch-safe materials, thoughtful mechanical keying and color-coding, and multiple assembly options make connectors with COEUR sockets good choices for applications from home energy storage and EV charging to the factory floor and data centers.