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→7.1.2.4 Electroless Deposition of Nickel/Gold
====7.1.2.4 Electroless Deposition of Nickel/Gold====
Electroless deposited nickel coatings with an additional immersion layer of gold are seeing increased importance in the coating of printed circuit boards (PCBs). The process sequence is shown in ''<xr id="tab:"/> (Fig. 7.2)'' using the example of the DODUCHEM process.
Tabelle
(DODUBOND process). This Pd layer acts as a diffusion barrier and allows the usage of this surface combination also for gold wire bonding.
As an alternative, for gold wire bonding applications a thicker gold layer of 0.2 – 0.5 μm can be applied using an electroless process. Typical electrolytes work at a temperature of approx. 80°C with deposition rates of 0.3 – 0.4 μm per 30 minutes. There are however limitations with these electroless electrolytes concerning their stability and the robustness of the process compared to other electroplating processes which reduces their wider usage ''<xr id="tab:"/> (Fig. 7.3)''.
Fig. 7.3:
