Rigid-flex PCBs require impedance testing

As a result of the differing signal behaviour between surrounding materials, the rigid and the flexible area must be considered separately when calculating the impedances in rigid-flex PCBs.

Würth Elektronik makes use of a special software which can calculate impedance models, as well as underlying design and material parameters in one step. Allowing everything to be seen very clearly, this software significantly benefits project documentation and the creation of the
PCB specification.

The software has the ability to take into account the crosshatching on the reference copper layer. When used with rigid-flex technology, crosshatching increases the impedance values using the same dielectric separation, improves bending behaviour (particularly under dynamic loading) and allows moisture over copper pads to escape more easily during the drying process before soldering.

Enabling complete monitoring of the signal behaviour, from transmitter to receiver, test coupons specially developed by Würth Elektronik measure impedances in the flex area. The rigid-flex measurement coupons are integrated into the manufacturing or delivery panel. Impedance can then be measured and logged before delivery to the customer.