4 Layer Flexible PCB Production Record #FPC-20260321-0034

This order comprised ten 4-layer flex PCBs built in panel format, each measuring 29 × 33 mm with an overall thickness of 0.23 mm. The stackup utilized rolled copper at ½ oz weight, 6/6 mil trace and spacing, 0.3 mm minimum holes, black soldermask, white silkscreen, and ENIG surface finish. Both polyimide and FR4 stiffeners were selectively laminated to balance flexure zones with stable mounting areas, requiring exact registration during material preparation and coverlay processing.

We performed stackup impedance engineering and trace width compensation prior to inner layer imaging and high-pressure lamination. Subsequent steps included solder mask application, electroless nickel and immersion gold deposition, followed by TDR impedance testing, dynamic flex testing, and 100% electrical verification. The thin construction and rolled copper demanded careful polyimide handling to prevent wrinkling or delamination throughout the 22.1-day schedule.

All panels met the specified impedance values and mechanical endurance requirements, confirming consistent layer alignment and reliable long-term flex performance for this impedance controlled flexible circuit.