Gold plating: Gold plating is a method of depositing a thin layer of gold onto the surface of another metal through plating way. The gold particles attached to the pcb, as strong adhesion also known as hard gold. The gold finger of memory bank is hard gold and abrasion resistant.
Immersion gold: Immersion gold through chemical reaction to make gold particles attached to pcb. As weak adhesion it is also known as soft gold.
Why use gold plating?
As IC become more and more integrated and IC pins are also denser. This brings difficulty to SMT placement. In addition, the shelf life of the HASL board is very short, so gold plateing board solves these problems:
However, as the circuit lines become denser and it brought short circuits. And as the frequency of the signal become higher, the effect of the skin that affect signal quality become more obvious.
Skin effect: High-frequency alternating current, the current will tend to concentrate on the surface of the wire.
Why use immersion gold?
In order to solve the above problems of the gold plating board, so adopt immersion gold technology:
- Due to the difference of crystal structure between Immersion Gold and Gold Plating, Immersion Gold is easier to weld than Gold Plating and will not cause bad welding. The stress is more easily to control.
- Since only pads has nickel-gold, the signal transmission in the copper layer in skin effect and will not affect the signal.
- Not easy to oxidation.