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NOVEMBER 2019 I PCB007 MAGAZINE 69 Impact of Dwell Time on Gold Deposition Timeway allowing, the dwell time is a tool for controlling the gold thickness specified by the end user. With thickness control in mind, a linear relationship between the thickness and plating time is advantageous. Figure 6 demonstrates that a statistical rela- tionship exists between dwell time and depo- sition thickness for the gold and is essentially linear; it displays the confidence intervals for pairwise comparisons of least squares means using Tukey-Kramer HSD. The statistical signif- icance is verified by the fact that the All Pairs Tukey HSD comparison circles are distinct and do not overlap each other. Given the fact that we could see larger comparison circles, the dif- ference is underlined in its significance. Impact of Temperature on Gold Deposition While the dwell times are used to configure timeway programs, the temperature is used for fine-tuning (Figure 7). Specified gold thick- nesses can be achieved in this way. Within the range tested, no statistical variation ex- ists in the deposition thickness. The tempera- ture range tested for this article was not broad enough to give a signal, but the optimum tem- perature of 68°C is significantly lower than the running temperature of comparative cyanide- containing baths that operate at >80°C. Impact of Bath Turnover on Gold Deposition Solution turnover is essential for filtration and can also be beneficial for cosmetic con- sistency. Production equipment often does not have the versatility to comply with supplier- recommended agitation. Figure 8 shows that the flow rate of 50 L/h and 250 L/h have no statistical impact on the gold thickness. Wetting Balance Result Wetting balance testing is a method to eval- uate wettability. Wettability is influenced by ageing, and the degree of degradation is of concern to manufacturers. In Figure 9, this de- terioration can be seen. The degradation is ex- pected and comparable to cyanide-containing immersion golds on the market. Nickel Corrosion Results Nickel corrosion is currently peaking in in- terest in the industry at present, with both fab- ricators and OEMs being involved. In Figure 10, all of the gold types and nickel types have been compared. The technique used was be- fore IPC-4552A discussions; however, many of Figure 6: ANOVA, the impact of the dwell time on gold deposition. Figure 8: ANOVA, the impact of bath turnover on gold deposition. Figure 7: ANOVA, the impact of temperature on gold deposition.