ILFA design rules for HDI PCBs
A. Plated Thruholesee figure I. on page 2Value
B. Buried Via
Minimum final diameterDepending on aspect ratio≥100 µm
Drilled diameterFinal diameter + 100 µm
Maximum aspect ratioDrilled diameter : via depth≤ 1:10
Minimum pad diameter outer layer up to 8 Layers≥ Final diameter + 300 µm
Minimum pad diameter inner layer up to 8 Layers≥ Final diameter + 350 µm
Minimum pad diameter outer layer > 8 Layers≥ Final diameter + 300 µm
Minimum pad diameter inner layer > 8 Layers≥ Final diameter + 400 µm
C. Standard Mircoviasee figure II. on page 2Value
D. Filled & Capped Mircovia
E. Copper filled Mircovia
Minimum diameter as formedDepending on aspect ratio≥ 100 µm
Maximum diameter as formed≤ 150 µm
Final diameter
Diameter as formed – (plating x 2)
Minimum capture land
Acc. To IPC-2226 A, Level B
≥ Diameter as formed+ 175 µm
Minimum target land
Acc. To IPC-2226 A, Level B
≥ Diameter as formed+ 150 µm
Maximum aspect ratio
Diameter as formed : Via depth
≤ 1:1
Filling level copper filled via
75 % - 90 %
F. Variable depth / skipped Microviasee figure III. on page 2
Value
Currently under development
G. Stacked Microvia see figure IV. on page 2
Value
Maximum cycles of stacked vias
4
All other values see: C. Standard microvias
H. Staggered Microvia see figure V. on page 2Value
Minimum staggered microvia pitch
≥ (Pad a + Pad b)/2
I. Layout on outer / inner layersee figure VI & VII. on page 2
Value
Minimum line / space
≥ 75 µm / ≥ 75 µm
Minimum distance wall to copper plated thruholes
≥ 250 µm
Minimum distance wall to copper microvia
≥ 162,5 µm
Minimum soldermask web
Green soldermask
≥ 80 µm
Minimum soldermask clearance
≥ 35 µm
Minimum soldermask overlapping (Soldermask defined pad)
≥ 35 µm
Your requirements violate our design rules? Please contact us. We will try to find an alternative solution with you.

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