Question 1

What is the difference between static and dynamic bend?

Accepted Answer

Static bend (install-to-fit) means the flex PCB is bent once during installation and stays in that position. Dynamic bend means the circuit flexes repeatedly during normal operation, like in a laptop hinge or printer head. Dynamic applications require much larger bend radii (100-200× thickness vs 6-15× for static).

Question 2

Why is RA copper better for flex PCB?

Accepted Answer

Rolled Annealed (RA) copper has a more uniform grain structure than Electrodeposited (ED) copper. This allows RA copper to withstand more bend cycles without cracking. RA copper is essential for dynamic flex applications and recommended for tight static bends.

Question 3

How does layer count affect bend radius?

Accepted Answer

More layers means a thicker overall stackup and increased stress during bending. Each additional layer adds to the neutral bend axis offset, requiring larger bend radii. Single-layer flex can achieve the tightest bends, while 4+ layer flex requires significantly larger radii.

Question 4

What happens if I bend tighter than the minimum radius?

Accepted Answer

Bending tighter than the minimum radius can cause: 1) Copper trace cracking leading to open circuits, 2) Delamination between layers, 3) Coverlay damage or cracking, 4) Reduced flex life for dynamic applications. Always design with margin above the minimum radius.

Question 5

How can I achieve tighter bends in my design?

Accepted Answer

To achieve tighter bends: 1) Use thinner materials (reduce PI and copper thickness), 2) Choose RA copper over ED copper, 3) Reduce layer count if possible, 4) Use adhesiveless (bondply) construction, 5) Avoid placing components or vias in the bend zone.

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