welding machine circuit board: 1.Shengyi base material 2.plating gold, 2-layers 3.free sample 4.best price and high quality Grandwork ... : Product Categories:single/double sided board, multi-layer board, high density board, including MLB with blind/buried via holesMain base ... FR-1, FR-2, FR-4, CEM-1, CEM-3, High Frequency Laminate with various dielectric constant (imported or from local supplier ...