... -turn prototype and mass production for 1-30 layer boards double sided rigid PCB Aluminum FR-4 LED PCB boardelectronic circui board ... 4 layer /double side printed circuit board /PCBinfo.Layer:4Material:FR-4Board finished ... ,Rigid-PCB,Flex-rigid PCB,HDI PCB ,PCB of single,Double and Multi-layers,High frequency PCB ,etc6)Max. finished board ...