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9th May 2019, Tewkesbury

Record printed circuit for UAV

A 26-metre long composite flexible printed circuit supplied by Trackwise. © Trackwise

A 26-metre long composite flexible printed circuit supplied by Trackwise. © Trackwise

Trackwise, based in Tewkesbury, UK, has shipped a 26-metre long composite flexible printed circuit (FPC), believed to be the longest ever produced, for distributing power and control signals across the wings of a solar-powered, unmanned aerial vehicle (UAV).

The circuit is one of over fifty supplied by Trackwise into this vehicle.

The entire interconnect system (power and signal) of the vehicle is made of FPCs, representing an estimated total systems weight saving of 60% over a traditional wire harness. This will enable the UAV, which is being manufactured in the US, to achieve higher payload and/or improved speed and range. The FPCs are manufactured using Improved Harness Technology (IHT), a patented, reel-to-reel manufacturing technique.

Conventional FPCs are rarely more than two metres in length, primarily due to limitations of manufacturing processes. IHT overcomes these limitations, enabling FPCs of unlimited length to be produced.

The UAV’s flexible circuit is based on a polyimide substrate. The planar structure of the circuit dissipates heat better than conventional wiring, enabling higher current carrying capacity for a given weight of copper conductor. Printed manufacturing ensures circuit consistency – fewer connection points are needed so reliability is enhanced, and the FPC is easier to install than wire harnesses, reducing a vehicle’s assembly time and cost.

“There are many new applications emerging for long, lightweight FPCs but aerospace is a natural fit,” said Trackwise CEO, Philip Johnston. “Weight savings, high reliability and cost-effectiveness are critical. We’re also seeing growing interest from a variety of sectors including medical and automotive. For the latter, manufacturers are challenged to reduce vehicle weight to improve fuel efficiency at a time when there’s an ever-growing array of electrical and electronic circuits in their vehicles. In particular, electric vehicles are accelerating this trend.”

Flexible printed circuit boards were developed 50 years ago as a replacement for wire harnesses – in order to save weight and space – and are now a multi-billion dollar global industry.

The application of flexible PCBs has however been limited due to the length of product available.  Due to manufacturers’ limits, product application has in general been limited to inside a box or equipment – rather than between boxes. 

A few PCB manufacturing process steps are static in nature and equipment used in these static processes defines the capability – drilling, imaging, pressing, plating.

The Trackwise innovation changes these static processes and makes them dynamic by i modification of existing PCB and roll-to-roll electrolaminate equipment and manufacturing techniques.

As a result of work carried out under a European Clean Sky research project, LHTFPCB – Large High Temperature Flexible Printed Circuit Boards – Trackwise (UK) and Rogers (Belgium) can now offer the large format flex PCBs, demonstrated to be capable of operating at temperatures up to 260ºC for long durations, even in high vibration environments.

As aero engines are designed to run hotter as part of a drive to increase efficiency, such high temperature circuitry offers the designer the ability to increase control of the engine.

Rogers has been developing a new material called XT/duroid laminate, which is based on polyether ether ketone (PEEK) material and can withstand some of the harshest temperatures and environments.

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