FR4 high-tg pcb board

Double side immersion gold circuit board without soldermask. Copper thickness 3oz finished. immersion gold 4U". Base material FR4 S1000-2. board thickness 2.0mm. 

The purpose of the Immersion Gold process is to deposit a nickel-gold coating with stable color, good brightness, smooth plating, and good solderability on the surface of the printed circuit. Basically can be divided into four stages: pre-treatment (degreasing, micro-etching, activation, post-dip), nickel, gold, post-treatment (waste water washing, DI washing, drying)