Samsung Patents a Stress-Resistant Flexible Circuit Board for Foldable Devices

By Patentlyze Team · Updated May 16, 2026

Every time you fold a Galaxy Z Fold, a thin strip of circuit board flexes with it — and Samsung is quietly engineering that strip to be a lot tougher. This patent zeroes in on the exact layered structure of the flexible PCB that crosses the hinge, with a new elastic element designed to survive the bend.

What Samsung's folding-hinge circuit board actually does

Imagine bending a paperclip back and forth a hundred thousand times. Eventually it snaps — and the same fatigue problem applies to the tiny circuit boards inside foldable phones. Every fold stresses the wiring that crosses the hinge, and over time that can degrade signal quality or cause cracks.

Samsung's patent describes a carefully layered flexible circuit board designed to handle that stress. The key addition is an elastomeric line layer — essentially a strip of elastic material — positioned along the hinge region. It sits aligned with a ground line (the electrical return path) and acts like a built-in shock absorber for the fold.

The rest of the stack is also carefully arranged: signal wires run perpendicular to the fold axis to minimize bending stress, and a shielding layer keeps electrical interference out. It's detailed, unglamorous engineering — but it's exactly the kind of thing that determines whether your foldable phone still works perfectly after two years.

How the elastomeric layer protects signals at the hinge

The patent covers the specific cross-sectional architecture of a flexible printed circuit board (FPCB) — the ribbon-like wiring that must physically bridge the gap between the two halves of a foldable phone as the hinge rotates.

The FPCB in the hinge region is built up in distinct layers:

• Substrate layer: the structural base of the flexible board
• Signal line layer: carries data signals and a ground reference line, both routed perpendicular to the fold axis to reduce mechanical bending stress on the conductors
• Shielding layer: a two-part EMI shield consisting of a shielding conductive layer (electrically tied to the ground line to drain noise) and a shielding insulating layer on top (to prevent short circuits)

The novel piece is the elastomeric line layer — a strip of rubber-like material embedded in the board, aligned with the ground line, in the section that physically passes over the hinge. Because the elastomer can stretch and recover, it absorbs the mechanical strain of repeated folding that would otherwise concentrate stress on the rigid metal conductors underneath.

The ground line and shielding conductive layer being directly connected is also deliberate: it creates a low-impedance path that cleans up electromagnetic interference (stray electrical noise) without adding extra layers or weight.

What this means for foldable phone durability

Foldable phones live or die by hinge durability, and the FPCB crossing that hinge is one of the most mechanically abused components in the entire device. Samsung's Galaxy Z Fold and Z Flip lines already advertise 200,000+ fold ratings, and innovations like this elastic reinforcement layer are how those numbers get pushed higher — and how signal integrity is maintained over the life of the device.

For you as a buyer, this kind of engineering translates to a phone that doesn't develop dead pixels, audio glitches, or connectivity issues after a year of daily folding. It's not a feature you'll see in a spec sheet, but it's a meaningful indicator that Samsung is continuing to invest in the fundamentals of foldable reliability.

Editorial commentary on a publicly published patent application. Not legal advice.