Most people think PCB fabrication requires a full chemical etching setup – ferric chloride, UV exposure units, transparency masks, the whole nine yards. But a diode laser and a bare copper clad board can skip half of that process entirely. Here is what is actually happening at the physics level when you laser engrave copper for PCB prototyping: • A focused laser beam (typically 450nm blue diode or 1064nm fiber) delivers energy density high enough to ablate or oxidize the copper surface • Copper is one of the most reflective metals at visible wavelengths, which means blue diode lasers struggle with raw copper – reflectivity sits around 60-65% at 450nm • Fiber lasers at 1064nm perform better but still face roughly 90% reflectivity on polished copper, which is why surface prep matters enormously • Coating the copper with a dry erase marker, flat black spray paint, or commercial laser marking compounds drops that reflectivity dramatically, allowing the laser energy to couple into the...