They look like covers at first glance but they aren't stickered on. I've never seen pads like this and searching doesn't bring up any results. Any information on these?

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1 Answer 1


It's a PCB finish, called Immersion Silver, or IS for short.

Some other common types of finishes:

  • Hot air-levelled solder (HASL) - Just your normal solder, levelled with hot air knives.
  • Electroless Nickel Immersion Gold (ENIG) - Your typical matte gold.
  • Galvanic Gold - Different type of gold finish, looks shiny and polished.
  • Organic Solderability Preservative (OSP) - Looks like bare copper.
  • \$\begingroup\$ AFAIK galvanic gold is actually galvanic nickel-gold, you still need a diffusion barrier just as with ENIG. \$\endgroup\$ Feb 19, 2016 at 8:30

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