4 Layer Flexible PCB Production Record #FPC-20250917-0076

This 4-layer flexible PCB measured 138.2 × 75 mm with a finished thickness of 0.23 mm and used rolled copper at ½ oz weight. Produced as single boards for a quantity of 30 pieces, the design featured tight 3/3 mil line/space geometry, 0.2 mm minimum holes, yellow coverlay, white silkscreen, and ENIG surface finish. A PI stiffener was applied, bringing the combined FPC + PI thickness to 0.31 mm.

DFM coordination confirmed the stackup tolerances of ±0.05 mm for both the flex core and the stiffened region. Silkscreen frames overlapping pads were removed to avoid interference with soldering. Gold finger areas were extended by 0.1 mm so the coverlay could fully secure the edges and reduce the risk of finger peeling during handling and assembly. These adjustments preserved the mechanical integrity of the thin flexible construction.

The revised coverlay registration and finger extension were implemented prior to production. Consistent ENIG plating and precise thickness control across the 4-layer flex structure were achieved, ensuring reliable flexibility and interconnection. The order was completed with full dimensional and electrical verification, delivering boards that met the specified thin-flex and stiffener requirements.