Surface Finish About Printed Circuit Board (PCB) 

LF HASL

lead-free Hot Air Solder Leveling Due to environmental concerns, the need for lead-free solutions.  To create the HASL finish, the printed circuit board will be submersed in molten solder (tin / lead). This solder will cover all the exposed copper surfaces. Upon retraction from the solder, high pressure hot air is blown over the surface through air knives, this levels the solder deposit and removes the excess solder from the board surface.

OSP 

Organic Solderability Preservative  

OSP is a water-based, organic surface finish that is typically used for copper pads. It selectively bonds to copper and protects the copper pad before soldering.

Immersion Tin 

Immersion Tin (ISn) is a good surface finish for planar, fine pitch products and is popular with press fit and backplanes.

Immersion Silver 

This is a surface finish whose benefits far outweight its costs. It gained widespread popularity since the RoHS and WEEE directive took effect, and can be a good alternative to ENIG for fine pitch and flat pack coating. It's a stable finish with a moderate shelf-life (roughly 12 months) and relatively simple process control.

ENIG

Electroless Nickel Immersion Gold It’s a double layer metallic coating, with nickel acting as both a barrier to the copper and a surface to which components are soldered. A layer of gold protects the nickel during storage.

HASL

HAL / HASL is well-established and understood by both manufacturers and end users. For a while though it looked like it would go out of fashion as a result of the use of components that need a particularly even surface this treatment could not guarantee.

Carbon Oil

Aurora has developed deep expertise in projecting carbon emissions under a range of future energy scenarios. This carbon modelling is tightly linked to our coal, oil and gas projections, as well as our industry-leading power market modelling

Gold Finger

 A row of square contacts neatly arranged on the edge of PCB are intended to plug into another matching socket of a main board to connect both PCBs and they are often dealed with gold-plating,this edge connector is called gold finger.

Tin-Plating

Tin plating is an industrial process where metal objects are coated with a thin layer of tin. This process can be applied to many types of base metals, including steel, iron, and copper. Tin plating improves the appearance of these metals for certain applications, and also helps to increase their performance and durability.

Flash Gold

Flash gold plating is less than 0.25 Microns and usually not done on connectors. For this purpose, Cobalt or Nickel hardened additives are used in the Acid gold bath and usually a thickness of >1.0 Micron gold is deposited and is subjected to tests such as contact resistance, wear resistance, porosity etc.

Gold Plating

Gold Plating is a method of depositing a thin layer of gold onto the surface of another metal, most often copper or silver (to make silver-gilt), by chemical or electrochemical plating.