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The main function of electroless nickel plating on printed circuit boards

Date:2019-01-21 18:07:59 Hits:632
There is a reliable electrical connection between the printed board components and the soldering robustness, which requires that the printed board surface be free of any form of contamination or metal oxidation. When the gold is deposited, the nickel layer is pure nickel without oxidation. Because of its chemical stability, it can be stored for a long time without oxidation, which ensures the solderability and appearance of the printed board.

Porosity

The electroless nickel plating layer has a lower porosity than the electroplated nickel layer of the same thickness. The acid plating solution has a lower porosity than the nickel layer deposited by the alkaline plating solution. The factors affecting the porosity are as follows.

(1) Thickness of electroless nickel plating

The porosity of the electroless nickel layer decreases with the addition of thickness. There is substantially no void when the thickness reaches 15 μm.

(2) Composition of electroless nickel plating solution

The addition of appropriate additives to the bath allows the coating to be crystallized while reducing porosity.

(3) Surface finish of the plated parts

The higher the surface finish of the plated part, the thicker the coating and the lower the porosity.

(4) Cleanliness of electroless nickel plating solution

In the electroless nickel plating process, continuous filtration is used to keep the plating solution free of suspended matter, impurities and precipitates, thereby reducing the porosity of the plating layer.

(5) Heat treatment of electroless nickel plating

Generally, after the electroless nickel plating layer is heat-treated, not only the hardness of the plating layer is improved, but also the porosity of the plating layer is remarkably lowered.

hardness

The hardness of the electroless nickel plating layer is very important for wire solderability, touch pad contact, printed circuit board plugs, and the like. The hardness of the electroless nickel plating layer is 2 to 3 times higher than that of the electroplated nickel, and the hardness can be improved after appropriate heat treatment.