This document contains tags and metadata for various types of printed circuit boards (PCBs) including double-sided and multilayer boards. It discusses factors related to choosing between 2-layer and 4-layer PCBs and lists tags for products like aluminum PCBs, boards with gold fingers or immersion tin finishes. The document also includes tags about PCB manufacturing processes, quality assurance, working with a fabrication company, and buying PCBs from RayPCB.