Finish coating may be metallic or organic. When choosing it, peculiarities of assembling process, set tasks and PCB design should be considered..
A coating is necessary to preserve PCB solderability, to ensure flatness and reliability of mounting of electronic components and solder joints. Pacific Microelectronics presents an optimal list of finish coatings.
Tin-lead HASL coating
HASL coated boards have a well treated surface and low cost. They are characterized by excellent solderability: connection strength is provided, the coating withstands a lot of soldering cycles. Drawbacks include lead content and nonflatness of contact pads. This method is not recommended for components with a step less than 0.5 mm.
LF HASL lead-free coating
This coating is characterized by a decent solderability and considered as a relatively inexpensive coating, so widely used. It withstands a wide range of thermal treatment with numerous temperature fluctuations. The coating is not recommended for products made with the use of high density interconnect technology, for SMD- and BGA-components.
ENIG immersion gold
The coating is deposited by chemical technique and looks like a thin gold film on the top of nickel underlayer. The gold provides excellent solderability (assuming correct choice of flux and soldering mode) and protects the nickel from oxidation. The advantage is uniformity of coating thickness. This treatment is recommended for mounting of components with a small step. The coating does not affect size of the holes. It is designed for multiple thermoloads. The disadvantage is possibility of "black site" defects.
The coating is compatible with all soldering techniques. It is characterized by good solderability. Immersion Sn meets the requirements for installation of components with a small step, used for connection using pressing technique. Does not contain nickel layer and, suitable for HF-boards. These boards should be stored in vacuum packing.
The surface features smoothness. This coating is recommended for boards with a small step. The recovery is possible. Cost of this coating refers to the average segment. The disadvantage is the need for handling with care, using gloves.
Organic protective coating
Excellent for PCBs with small steps, small components, BGA. The coating is characterized by high smoothness and relatively low cost, possibility of recovery. Need for special delicate handling is a disadvantage of this technology. Shelf life is limited.
In our manufacture you can order following coating
In our manufacture you can order following coating: