6 Layer 2+N+2 HDI PCB Stacked Laser Vias 0.4mm BGA Fanout Hard Gold Finger High Tg 170

A two-plus-two build-up over a four layer core gives this board six routing layers in a 1.2 mm package. Two sequential laser via levels are stacked directly on the buried through vias, so signal paths stay short and the return current never has to leave the plane. The hard gold edge fingers are built for connectors rated for repeated insertion.

Build-up sequence

1. Four layer core laminated with high Tg 170 FR-4, copper 1 oz on inner layers
2. First laser level: 0.1 mm microvias filled with copper paste and planarised
3. Second laser level stacked on the first via landing, no via-in-pad offset allowed
4. Outer layer imaging at 0.05 mm line and space, then hard gold on the connector area

Reliability data

Electrical and thermal envelope

Impedance control +/-5 percent on 100 ohm differential pairs. Dielectric loss is held under 0.012 at 5 GHz with the selected laminate. Thermal conductivity of the cured stack supports 2 W per module heat spread through thermal vias at 0.5 mm pitch. Glass transition 170 C with decomposition temperature above 340 C, suitable for lead free reflow with three passes.

Capability summary

• Six layers, 2+N+2 sequential build-up, board thickness 1.0 - 2.0 mm
• Laser via 0.1 mm, stacked via option, 0.4 mm BGA pitch fanout
• Min line and space 0.05 mm / 0.05 mm on outer layers
• Surface finish: hard gold 1.27 um on fingers, ENIG elsewhere
• Max board size 400 x 500 mm, warpage 0.35 percent maximum
• Target markets: automotive radar modules, infusion pumps, industrial cameras, base station RF front ends

Documentation delivered with each lot

Stackup drawing, impedance coupon TDR report, microsection photos of each laser level, IST or thermal cycling data on request, and a first article inspection report for new part numbers.