ELI5 Why where old PCBs brownish/beige and now they are green?
In: Chemistry
Old PCB’s were mostly green. The colored part is the solder mask, which is the top/outside layer that protects the conductive traces. Green is chosen as it causes less eye strain, which is helpful to the ones who stare at these boards 8 hours a day. It is also likely chosen since the resin is made it bulk, so it’s cheaper.
Power supplies seem to use boards with no solder mask likely due to them needing solder traces (As they may be inadequate in their current carrying capabilities), and only using jumpers/wires. The tan/yellow color of the substrate is visible since there’s no solder mask covering it. Older and simple electronics would sometimes use this method too.
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