The Difference And Difference of The Color of The Circuit Board Solder Resist Layer

Green: Most common, low cost; good UV light transmission, beneficial for exposure process; high contrast of lines, easy to detect defects.
Black:earance is high-end, but low reflectivity, difficult for visual inspection; slightly higher heat absorption (extremely small impact on heat dissipation)
White: High reflectivity, for LED lighting; shows dirt easily, requires strict cleaning process
Blue: Good contrast (second to green), often used for industrial control equipment; better dirt resistance than white.Red/Yellow: High recognition, often used for power modules or test boards; poor UV light transmission,
Transparent (no solder resist): No solder resist layer copper foil exposed; only used for special tests or high-frequency signal debugging.

Core factors influencing color variation
1. Manufacturing process
Ultraviolet exposure: Green solder resist ink has high sensitivity to ultraviolet light offering the best imaging precision and highest yield.

Coating uniformity: Dark (e.g. black) inks tend to have uneven coating, requiring higher process control

Thickness difference: White ink may require a thicker coating to cover the base material, affecting the precision of fine-pitch pads.

2. Inspection and maintenanceVisual inspection: The contrast between the copper traces (light yellow) and the solder resist layer is clear on green boards, allowing for efficient manual inspection; black boards rely on AI (automatic optical inspection).

X-ray inspection: Color does not affect X-ray penetration, but dark-colored boards can be more challenging to repair due to-of-sight obstructions.

3. Thermal management
Theoretical impact: Dark (black/blue) colors absorb slightly more heat, while light (white/) colors have higher reflectivity, but the actual temperature difference is less than 1℃ and can be negligible.

Key factors: Heat dissipation primarily depends on the thickness of copper layer and the design of thermal vias, not the solder resist color.

4. Cost differences
Green: Standardized production, lowest cost (¥0.~1/piece, double-sided boards).

Black/white: Requires special inks, increasing costs by 20%~50%.
Niche colors (red/yellow): Smaller batch sizes can lead to a doubling of costs.