HASL /Electroless Nickel Immersion Gold (ENIG)
Refer to past projects, the most popular surface finish choices of customer is HASL,as its low cost and robust, fundamental changes in the PCB industry—namely, the rise complex surface mount technology—have exposed its shortcomings. HASL leaves uneven surfaces and is not suitable for fine pitch components. Although it does come in lead-free, there are other lead-free options which will likely make more sense for a high-reliability product.
ENIG is quickly becoming the most popular surface finish in the industry. 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. ENIG is an answer to major industry trends such as lead-free requirements and rise of complex surface components (especially BGAs and flip chips), which require flat surfaces. But ENIG can be expensive, and at times can result in what is commonly known as “black pad syndrome,” a buildup of phosphorous between the gold and nickel layers that can result in fractured surfaces and faulty connections.
Recently the cases to dip conformal coating are more popular, conformal coatings protect your electronic printed circuit boards from moisture and contaminants, preventing short circuits and corrosion of conductors and solder joints.
They also minimize dendritic growth and the electro-migration of metal between conductors.
In addition,conformal coatings protect your circuits and components from abrasion and solvents. Stress-relieving is also provided, as well as protection of the insulation resistance of the circuit board.