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I see lots of PCB trace antennas in green color layer, as I know the dielectrics. On the other hand, there are FPC antennas (flexible printed circuit board antennas) are mostly in somehow black color, more like the antennas covered with black enclosure, I can’t estimate. What’s the exact reason they prefer it to be in black? Any performance difference might be? Any drawback of this black modules? I leave a link below for a sample of that. Please check it out. I’d like to get ideas what would be the drawbacks of using this types.

antenna sample

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  • \$\begingroup\$ The green color on a PCB is the solder mask. These days it can be almost any color you want, including black. There is no performance difference between the colors. \$\endgroup\$
    – Lior Bilia
    Commented Oct 20, 2023 at 17:40
  • \$\begingroup\$ @LiorBilia Not sure I believe the "no performance difference", especially when RF is involved. I wouldn't be surprised if at microwave frequencies the soldermask can become significant--certainly in the dozens of GHz at least. The color may not directly affect it, but I bet there are slight differences in dielectric constant between formulations. \$\endgroup\$
    – Hearth
    Commented Oct 20, 2023 at 17:55

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The color is arbitrary; materials are available in all colors with high and low RF losses. I would think there is very little that can be told visually.

Coverings/coatings are thin, so have relatively little effect on the fields, which are mostly in the air above, little actually in the layer. The loss may still be important for high-Q (compact, narrowband) antennas, or low loss (high efficiency, low noise?), which is why soldermask is usually removed around RF components on PCBs for example.

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