Electronic – Why is the PCB part number traditionally on a copper layer

coppersilkscreen

I'm an experienced board designer, having designed 100+ boards over the past decade, and I have yet to hear a good answer for why the PCB part number is traditionally on an external copper layer, and the PCBA part number is on a silkscreen layer. To me copper is always "sacred" and should not have anything unnecessary on it, as this can screw up voltage isolation, RF performance, etc. But for some reason designs tend to have the bare PCB part number in copper instead of silkscreen. Why?

Best Answer

Copper etching is a very early step in the PCB manufacturing process. Etching the board number on the copper layer allows identification of the board at all subsequent stages. To omit it would risk confusion due to lack of a board identifier.