Trackwise initially developed the capability to manufacture length-unlimited, flexible circuits because of a requirement from Rolls Royce. In an interview with Power Electronics News, Philip Johnston, CEO of Trackwise, said that using long, flexible printed circuits in aircraft could help address the weight and space challenges associated with legacy wiring harnesses.
Trackwise long flex is being used for temperature- and voltage-monitoring circuits for electric-vehicle battery packs. In place of conventional wire harness, flex offers a lighter solution taking up less space — and potentially for distribution of control electronics onto a “smart harness.”
“With the battery pack in the electric vehicles being the primary energy source, control and monitoring of individual cells and modules are paramount. This is not only for safety reasons, but also to achieve optimum performance efficiency and the maximum range. Flexible printed circuits (FPCs) are ideal for use in the control and monitoring circuits of battery modules. Not only do their compact dimensions offer significant space improvements, but the weight savings are considerable compared to bulky harnesses,” says Johnston.
He added, “Trackwise’s roll-to-roll technology is already being used to manufacture FPCs used in the HV and LV circuits of EV battery modules and packs, reducing assembly time, BOM costs, and saving on space and weight.”
PCB design
FPCBs are manufactured using photolithographic technology. An alternative way is to laminate very thin copper strips (0.07 mm) between two layers of polyester (PET). These PET layers, typically 0.05 mm thick, are coated with an adhesive that is heat-cured during the lamination process. The main advantage is the ability to flex electrical connections during normal operation, such as between subsystems to replace wiring in, for example, aerospace and automotive.
In many areas of electronics, we are witnessing a growing demand for higher-performance products with ever-smaller dimensions and weight. These stringent requirements call for PCB solutions capable of accommodating high densities of electronic components in ever-tighter spaces. The automotive industry offers many significant examples of the potential use of FPCBs, including steering wheel and dashboard control systems, displays, infotainment and audio systems, pushbuttons, rotary encoders, and more. These applications require high reliability, robustness, and simplicity of wiring to minimize soldering, which can potentially lead to oxidation or false contacts due to aging and mechanical stress. Devices based on FPCBs offer high resistance even in the presence of high vibrations and shocks, are less prone to faults, and have lower weight and higher circuit density.
In an EV, the battery management system (BMS) monitors the status of the batteries during operation. Intelligent functionality is needed to prolong the life of the batteries, which has a fundamental impact on the total cost of ownership. The battery management system must continuously monitor the health status, charge level, and depth of discharge. As batteries age, the varying health of individual cells can correspond to a change in nominal capacity: The challenge is to optimize the use of cells through a supervisory circuit that ensures a balance — active or passive — of energy levels during operation. Flexible circuits provide the perfect lightweight and compact method of connecting each cell’s sensors to the BMS.
Improved Harness Technology
A patented process innovation* has extended Trackwise’s capability to the manufacture of flexible multilayer PCBs of any length, making these the world’s largest flexible multilayer PCBs. Many traditional PCB manufacturing process steps are fixed, such as drilling, screen-printing, pressing, and plating. Trackwise’s innovation changes these static processes and makes them dynamic; innovative modification of existing PCB and roll-to-roll electrolaminate equipment and manufacturing techniques. The outcome of this is that, rather than the supply chain and manufacturing process defining the limits, the only limit is that of the application itself.
