#flex pcb

The number of processes required for rigid-flex sheets is more than three times that of flexible sheets, and the scrap rate is comparable to that of multilayer sheets.

For some flexible sheet applications with very small bending radii, a gradually increasing design is required. This is often used in multi-layered flexible sheets, where the length increases from the inside out according to the bending direction to avoid bending wrinkles.

Common defective or scrapped rigid-flex PCB quality issues include substrate voids in the extended area—voids or bubbles in the dielectric structure—greater than 3 mils or interfering with conductor-to-conductor space, rendering the PCB unusable.

Rigid-flex PCBs require extremely stringent quality control. The biggest challenge comes from thermal stress, which may necessitate representative plated via attachment cutting, visual inspection, and cross-sectional analysis.

After the plated hole area is completed, an additional flexible plate and cover plate layer are used to seal it inside the thicker rigid-flex plate. Finally, after the master plate is laminated, the process proceeds to the second plated hole process.

To create a multi-layered structure in the plated hole area, a layer-by-layer sequential lamination method must be used. First, a thinner layer is applied, followed by the final rigid-flex plate stack.

The flexible board is then laminated as a single sheet into subsequent processes. Tooling systems for the edges and scrap areas can be used to assist in alignment and thickness control.

The edges of the flexible board may not be attached to other parts in the final product, making interface cutting quite difficult. Pre-cutting with a die is necessary.