4 Layer Flexible PCB Production Record #FPC-20260729-037

This production run delivered five 4-layer flexible boards measuring 63 × 63 mm with an overall thickness of 0.32 mm. The boards were built on polyimide using 0.5 oz rolled copper, PI stiffeners in designated areas, 6/6 mil minimum trace and spacing, and 0.3 mm minimum holes. Yellow soldermask paired with white silkscreen created high visual contrast, while immersion gold ENIG surface finish provided stable pad surfaces for soldering and long-term contact reliability on this thin multilayer flex design.

Material preparation emphasized careful polyimide handling to maintain flatness prior to inner layer imaging, etching, and stack alignment. High pressure lamination bonded the four layers accurately, after which coverlay lamination, solder mask application, electroless nickel deposition, and immersion gold deposition were sequenced to preserve flexibility while ensuring uniform plating thickness across the circuit.

Dynamic flex testing and 100 % electrical testing verified circuit integrity under repeated bending cycles and confirmed all five boards met specified performance criteria without deviation. The executed process sequence produced consistent results across the complete small-quantity order, supporting dependable operation in the intended flexible application.