Issue link: https://iconnect007.uberflip.com/i/1533339
16 PCB007 MAGAZINE I MARCH 2025 • Level 2: Any other observations • Level 3: Ten or more events, with more than five deeper than 40%, or surface corrosion affect- ing more than 30% of the image is method allows for the clas- sification of corrosion for a single plated-through hole (PTH) and the comparison of individual PTHs. To elaborate and provide an overall compari- son of multiple panels under different condi- tions, a second rating system was introduced. It collects and relates results from all evaluated PTHs per condition, enabling a comparison between panels. e occurrence percentages were calculated and identified, with the fol- lowing assumptions: • Corrosion rating 0: No corrosion • Corrosion rating 1: More than 60% of investigated locations have a Level 0 or 1 • Corrosion rating 2: All other observations • Corrosion rating 3: More than 40% of locations show a Level 3 e corrosion rating system also considers the criticality of certain corrosion types, such as surface corrosion, which poses the highest risk for defects in the final assembly finish. To enable a direct comparison of conditions across different plating companies, test panels with the same design were distributed to vari- ous sites. ese test sets were evaluated at four different PCB shops located in Europe, the USA, and China. e gold bath types used by these manufacturers spanned all three types of gold electrolytes, from I to III. e test over- view is displayed in Table 3. In Figure 3a, the comparison of the differ- ent levels which were observed at the different plating sites is shown. In 3b, the results of the rating considering the percentage of the level findings for each location is summarized. e evaluation of ENIG corrosion across various PCB shops in the U.S., Europe, and Asia revealed significant variability in results, influenced by multiple factors beyond just the type of gold electrolyte used. is comprehen- sive study highlighted the following key points by the same trend of results for both corrosion levels and rating: • e gold bath Type I showed a high ratio of Level 1 and Level 2 corrosion. Although ENIG corrosion events were present, they were limited in number and depth, indi- cating that controlled corrosion within defined ranges does not necessarily nega- tively impact solder connections. Table 3: Overview of test IDs and locations 2 Figure 3: Corrosion result as a) Levels at manufacturers A to E; b) Corrosion rating at manufacturers A to E 2 . a b