It’s significant that the final substrate materials has copper on either side to make it suited to a double-sided style. With the strict prerequisites for higher precision in PCB fabrication system, line width and spacing have underneath 0.1mm. Gold-plating board is easier to produce short circuit than immersion gold board. https://beckettrwyzb.ageeksblog.com/30204308/copper-based-pcb-for-led-an-overview