Dear Sirs,
I can not find the info about the number of bending cycles or similar parameters for electrical parameters change for flexible printed circuit board (pcb) with teflon/ptfe substrate. For example flexible pcb of Rogers corp.
Thank you for an advance
The reasons for the lack of a # of bending cycles are manifold, as the "lifetime" of a flexible circuit is determined by a lot of factors:
- design parameters: thickness of PTFE (or polyimide) layers, thickness of copper layers
- layout parameters: copper "fill factor", number, diameter and location of eventual vias
- operating temperatures
- bending radius
- ...
From general experience: a single-layer linear flexboard (effectively replacing some cable) is expected to survive millions of bending cycles (think of the flexboard connecting an ink jet's printing head with the electronics), while a design involving complex geometries and multiple layers might fail after a 2-digit number of bending cycles.
Not to be forgotten: part pads might be suscepted to shear, easily peeling off.
Thank you for reply. But for single layer flexboard what bending radius do you mean (1000 000 cycles)? What is happened if I bend the pcb at the radius of 2 pcb thickness?
Teflon substrate is badly adgesive. For this teflon pcb the bending radius will be more large than for some other plastics?
What alternatives of flexible pcb are if we need high flexibilty, high frequency (100-3000 MHz)? Woven harness/cable or more precisely electric woven circuits are presented in commercial market?
1 000 000 cycles? I've seen a bending radius > 10 mm in a printer application. Hardly expressable in multiples of flex thickness.
Repeated bending at a too low radius might result in breaking the traces and/or breaking the substrate. Delamination might occurr at low, but not too extremely low radii and is well-known for PTFE and polyimide.
Alternatives? Eventually some highly flexible coaxial cable rated for such applications. At generous bending radii. (Typically > 10 cable diameters an above. See manufacturer's recommendations.)
You may check e.g. Lapp ( https://www.lappkabel.com ) for the availability of appropriate cables.
But if I need conductors are distributed in plane - flat cable, no braid (no shielding), high frequency >100MHz ? Could you advise some manufacturers?
In plane? Which nominal resistance?
(Although the typical ribbon cable might not be fit for continuous bending.)
Meanwhile I checked with Lapp (site was unresponsive this morning): coaxial cables for continuous bending are rare anyway: they have a single type for RGB transmission (3 coaxial cables in a single sleeve) with 11 mm outer diameter and 15 outer diameters bending radius.
For research purposes I need flat cable (without shielding) of large width 3-15 cm. Is it possible to buy such cable? I heard that there is woven harness, ribbon e.g. for spacecraft applications. How is it effective at 30 MHz and more?
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