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Differences in adhesives between flexible boards and rigid-flex boards: Rigid-flex boards require more adhesive to fill the gaps between circuit lines during lamination.

The manufacturing process of rigid-flex boards differs from that of flexible boards. Only by creating a flat, smooth surface can good pattern transfer be achieved. A flat surface also helps improve drilling accuracy.

Adhesive-free materials offer higher stability than traditional flexible sheet materials, with glass transition temperature and coefficient of thermal expansion similar to rigid sheet materials, making them suitable for producing high-layer, high-density rigid-flex sheets.

Using adhesive-free materials to manufacture flexible sheets can reduce the cost and quality issues associated with conventional lamination and inner layer processing.

All flexible board adhesives must be excluded from the rigid area and plated hole area. This requires the use of special substrates, window processing, and pure film embedded in the flexible area.

The protective film and adhesive should be excluded from the plated holes of the flexible board, and window openings and adhesive sheets can be used instead.

The flexible sheet is manufactured using traditional methods, with the protective film only applied to the bending areas; the rigid areas are still bonded using epoxy resin adhesive sheets.

Traditional flexible board adhesives expand significantly upon heating. If acceptance testing, including stress testing, is only performed on rigid plated hole areas, it is better to avoid using adhesives with high plasticity and low cross-linking density.

Traditional acrylic resins and modified epoxy resin systems are relatively inexpensive materials that can meet the needs of low-layer, thin copper foil product manufacturing processes.

Many rigid-flex panel layers are laminated together using flexible sheets, which include acrylic resin and coated adhesives.

The cover plate is a reinforcing material that reduces the impact of assembly stress on the rigid-flex panel. Occasionally, some appearance quality issues may occur, such as exposed texture or scratches.

Lamination does not require substrate treatment; it only requires ensuring good adhesion of the pre-treated metal surfaces.

Surface treatment: Oxygen-plasma treatment is a good method because it dries the surface, avoids exposure to foreign matter, and improves adhesion.

Acetone cleaning carries some risks, but it is quick and effective. It should be done a few minutes before lamination. Be careful to avoid using solvents containing water, as acetone is hygroscopic; the boards should be kept sealed.

Sandblasting roughens and passivates smooth surfaces to improve mechanical bonding. It should ideally not be used on exposed areas of finished flexible boards, as this may cause quality problems.

Surface treatment before lamination: oxygen-plasma treatment; sandblasting; acetone cleaning; pre-coating with adhesive.

When fabricating adhesive-coated rigid-flex boards, the adhesive on both sides should be removed. If necessary, glass fiber etching may be required to improve copper adhesion.