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28 PCB007 MAGAZINE I OCTOBER 2024 the shelf life and solderability following mul- tiple soldering operations. Copper atoms read- ily diffuse through porous gold layers, reduc- ing solderability and increasing contact resis- tance. at said, DIG has several notable features: • e intermetallic during solder assembly is copper-tin, a well-understood and reliable interface. e intermetallic is less brittle than nickel-tin and better suited for appli- cations involving mechanical stress, such as bending and twisting. • Removing electroless nickel from the deposit stack improves high frequency circuit performance where EN's magnetic properties increase insertion loss and high speed signal attenuation. • e removal of the nickel is valuable in fine pitch line-and-space design where the thick nickel diffusion layer (200 min) reduces spacing. • e process is less expensive than the premium final finishes of record: ENIG and ENEPIG. e DIG process is particularly advantageous for high-frequency designs where assembly processes are less complex, and shelf-life sol- derability is not a concern. DIG is not suitable for long-term storage and solderless connec- tion applications. What applications and PCB technologies are using RAIG? PWB manufacturers with ongoing, high- volume ENEPIG customers benefit most from RAIG because RAIG is particularly well suited to plating consistent thicknesses of gold on electroless palladium. As previously men- tioned, the lower electrochemical reactivity of gold and palladium makes the autocatalytic feature of RAIG gold singularly useful. By building gold thickness on palladium autocatalytically, deposition rates and corre- sponding thicknesses are optimally uniform and predictable. Overall, RAIG gold deposits exhibit a tighter grain structure, resulting in less gold porosity. It has been noted by a num- ber of OEMs that lower ENEPIG gold poros- ity increases connection reliability for solder- Table 1: Nickel hyper-corrosion cross-section