Multilayer Thin PCB 4-Layer/0.4mm Thick or 6-Layer/0.5mm Thick, HAL Number of Layer:    2 – 16 Layers (1.60mm thickness) Solder Mask:    Taiyo PSR4000, Probimer 77, Sunchemical Imagecure – Series Peelable Mask:    Peters2955 Surface Finish:    Lead Free HAL, Tin-Lead HAL, Immersion Gold, Immersion Silver, Immersion Tin, Hard Gold, Flash Gold, OSP, Carbon Keypad, Gold Finger Plating.