DuPont Streamlines Bus Bar Overmolding for High-Voltage EV Components

A combined material-process-service solution based on Zytel HTN polyamide delivers on battery-performance parameters.

DuPont Mobility & Materials is breaking new ground for manufacturers of xEV components with a combined material-process-service solution for overmolding bus bars with Zytel HTN polyamide (PA) material. Bus bars are a workhorse component essential for distributing power in xEV batteries, motors, and power electronics. distributor busduct

Overmolded bus bars are found in virtually every xEV system. They transfer electrical energy from high-power battery packs to inverters, and inverters to e-motors, while insulating the conductor from ground or other phases. With the right materials, a bus bar can enhance a battery or e-motor energy density, durability, and electrical safety. However, it must be adequately insulated if the battery overheats, a condition known as thermal runaway, to help avoid module-to-module heat propagation.

“Although small, bus bar components are numerous, and also critical to the efficiency and durability of xEV batteries, motors, and power electronics,” said Giacomo Parisi, Marketing Director for Automotive Electrification at DuPont. “Our goal is to provide an excellent material for the application, along with assisting customers in their bus bar design and overmolding, to help them achieve their performance and production goals.”

Bus bars within xEV batteries must meet several requirements, including:

Resistance to thermal runaway without loss of function;

qualification via demanding thermal cycling and electrical tests;

efficient production to reduce manufacturing time and cost;

stable orange color to indicate high voltage, even after prolonged exposure to high temperatures.

Leveraging a host of production equipment, lab testing, and engineering capabilities, DuPont has fine-tuned an overmolding process for bus bars that incorporates Zytel HTN material along with robust technical and processing support. Using sophisticated computer-aided analysis tools, DuPont collaborates with customers to reduce manufacturing time and cost yet maintain performance and safety standards.

Zytel HTN has been identified as an elegant material solution in this area. For example, safety standards dictate that bus bars maintain a stable orange color indicating high voltage, even after repeated exposure to high heat. Zytel HTN accelerated aging tests show no noticeable color shifts, even at 130°C. It also contributes insulative properties for safer thermal runaway, and easily overmolds onto aluminum or copper, the most common bus bar metals.

Additionally, Zytel HTN insulation materials for bus bars resist multiple thermal shock cycles (typically 1000 cycles) at temperatures (-40° to 150°C) normally needed for motors and power electronics applications. This means the material resists cracks after being overmolded onto metal conductors. Further, the material is chemically resistant to the fluids used for thermal management and has a high comparative tracking index (CTI) at elevated temperatures.

DuPont Mobility & Materials will showcase these and other innovations at K 2022 in Düsseldorf, Germany, from Oct. 19 to 26. The company is exhibiting in booth C43 in Hall 6.

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