Engineering process of PCB conformal coating has been dramatically changing in recent years and a variety of PCB conformal coating spring up with development and enhancement of PCB assembly technolgy. In general, conformal coating prevents oxidation and contamination of pads on PCB, electrical conjuction and electronic components and meets assembly requirements under high temperature to ensure relaibility of soldering.
Categories of PCB Conformal Coating
HASL is tyically applied all over the world, which can meet requirement of wave soldering, particularly on occasion of high soldering intensity. However, we are hunting for new coating technology to replace HASL drived by increasing requirements of lead-free engineering process.
OSP (Organic solderability preservative) is an organic coating, preventing copper oxidation before soldering and ensuring the pads are not damaged. The weakness of OSP is that it will be easily melted and copper comes out generating metallic oxide during re-flow soldering with climbing temperatures.
ENIG is to plate Ni/Au on the copper surface by chemical methods. After plating Ni and Au, the barrier layer is formed between Ni and copper. PCB surface treated by ENIG is very smooth and in good planarity, typically used for key contacting surface.