4 Layer Flexible PCB Production Record #FPC-20260210-0025

Manufacturing this batch of 4-layer flexible PCBs involved a 0.2 mm thin stackup using 1/3 oz rolled copper and 3/3 mil trace spacing across the narrow 285 × 40 mm single-board format. The specification included yellow soldermask, white silkscreen, FR4 stiffeners in designated areas, and immersion gold ENIG finish. Impedance characteristics were addressed through stackup engineering and confirmed with TDR testing, requiring exact registration on the thin polyimide material.

Material preparation and inner layer imaging were followed by trace width compensation during etching to achieve the target geometries. Layer stack alignment, high pressure lamination, coverlay application, and solder mask processing were sequenced to protect the flexible layers. We performed dynamic flex testing alongside full electrical testing, verifying both mechanical endurance and circuit integrity across all 10 boards.

Completed over 12 days, the run produced consistent results that met every tolerance for this impedance controlled flexible PCB. The combination of fine features, light copper weight, and non-standard mask color on such a thin construction demanded precise process control at each stage.