Layer:10
thickness:1.6mm
gold thickness:40um
gold finger:printdecircuitboard
The surface mostly has three colors: dark green, orange-gold and white.
As I understand, the green is resist, the orange-gold is copper, and the white just the silk screen.
I find it surprising the color of the PCB's surface copper is quite different to the color of copper pipes. Please compare the orange-gold of PCBs, and the reddish-orange of copper pipes.
Because that board has been gold plated. Ironically, that saves money; copper tarnishes, and would need expensive cleaning immediately before soldering. And gold on the contact fingers makes for reliable connections. Other platings are possible : tin or silver, and formerly lead-based solder. Scrape some green solder-resist off the earth track and you would see a more reddish metal, though it would take a few months to tarnish to the colour of those pipes.
