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76 PCB007 MAGAZINE I MARCH 2025 rior performance compared to higher Au thickness (ENIG) in terms of the insertion loss which can be explained by more signal passes through Au layer in thicker Au (ENIG) instead of electroless Ni (NiP) layer. Intermetallics: Direct Immersion Gold (DIG) Comparison is comparison was conducted to see how a sample with the barrier layer compares to sam- ples without any barrier to intermetallic growth. e references for DIG surface finishes in Table 2 included different testing parameters, including only one or two reflow, respectively, instead of the six reflow cycles that the Ni- less surface finish samples in the current study were subjected to. In addition, the referenced studies used surface finishes with thicker gold. Finally, the second 11 used temperature cycling instead of heat storage, but the 10 used heat stor- age for 1,000 hours at 150°C, the same as the Ni-less surface finish samples. However, despite the harsher sample prep- aration for the Ni-less surface finish samples in the current study, the results in Table 2 show that the Ni-less surface finish has consis- tently thinner intermetallics than the DIG sur- face finishes. is data is as expected since the Figure 8: Insertion loss comparison between EPIG and Ni-free surface finish. Figure 9: Insertion loss comparison between ENIG, EPIG, and Ni-free surface finish.