Definition

Coverlay is a polyimide film with adhesive backing that's laminated over flex circuit traces as a protective covering, serving the same function as solder mask on rigid PCBs. Unlike photo-imageable solder mask, coverlay is mechanically punched or laser-cut to create openings for pads and vias before lamination. Coverlay is more flexible and durable than liquid solder mask on flex circuits, essential for dynamic flex applications. Typical thickness is 25 µm polyimide plus 25 µm adhesive.