无标题

Rigid-flex panels differ from other multilayer boards in that the layers are not necessarily continuous, requiring pre-cutting, shaping, and grooving of the edges.

Most rigid-flex panels are made from raw materials derived from rigid and flexible sheet manufacturing processes. The specific processes involved in rigid-flex panels only begin to take effect from the lamination of the master sheet.

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.

The filler material is also placed in the open areas during pre-stacking, serving the following functions: preventing adhesive (bonding sheet) flow; and maintaining minimal torsional deformation.

The filler material is placed in the open areas during pre-stacking, serving the following functions: filling cavities to equalize bonding pressure; and preventing interlayer bonding of the flexible sheet.

Window cutting commonly uses a die-cutting mold, which aligns with the adhesive layer or bonding sheet through tool holes and pins to precisely cut out specific areas.

Before the flexible sheets are laminated, the cover plate, each layer of flexible sheet, adhesive sheet, or bonding layer must be pre-cut with tool holes, windows, slots, and local shapes.

In a rigid-flex PCB, the cover plates and flexible PCBs are securely attached together and extend into the rigid area, which contains the plated holes.

A common rigid-flex PCB structure consists of one or more flexible PCBs sandwiched between two sets of rigid cover plates. The cover plate area remains wire-free and is eventually removed.

The interconnection area between the flexible and rigid regions can absorb minor misalignment and provide the flexibility required for assembly.