PCB Legend (Silkscreen) Parameters

The silkscreen layer provides text, logos, and component identifiers on the PCB.

Key Specifications:

Ink Type:

Epoxy-based ink: Most common, cured thermally or by UV.

LPI (Liquid Photo-Imageable): Higher resolution (for fine text).

Color: Typically white (also available in black, yellow, etc.).

Line Width/Resolution:

Standard: ≥0.15 mm (6 mil).

High-precision (LPI): 0.1 mm (4 mil).

Font Height:

Minimum: 1.0 mm (standard), 0.5 mm (high-density designs).

Curing: UV or thermal curing (150–200°C for epoxy ink).

Legibility: Must resist fading during soldering and cleaning.

Solder Mask Stencil Parameters

The solder mask layer insulates copper traces and defines solderable areas.

Key Specifications:

Material:

LPI (Liquid Photo-Imageable) solder mask: Most common (epoxy-based).

Dry film solder mask: For high-precision designs.

Color: Green (standard), also red, blue, black, etc.

Thickness:

Standard: 10–25 µm (after curing).

Via tenting: Thicker to cover holes.

Resolution:

Minimum clearance: 0.05 mm (2 mil) between mask and pad.

Bridge width: ≥0.1 mm (4 mil) between pads.

Curing: UV exposure + thermal curing (150°C for LPI).

Dielectric Properties:

Withstands soldering temperatures (260°C+ for lead-free).

Insulation resistance: >10⁸ Ω.

Parameter Silkscreen (Legend) Solder Mask Solder Paste Stencil

Material Epoxy/LPI ink LPI/Dry Film Stainless Steel

Resolution ≥0.1 mm ≥0.05 mm ≥0.1 mm aperture

Thickness N/A 10–25 µm 0.1–0.15 mm

Curing UV/Thermal UV/Thermal N/A

Key Function Component marking Insulation Solder paste deposit