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88 The PCB Magazine • August 2017 sistance is >10% over the established base- line on either circuit, it is considered a failure and the test is halted. Material type and com- plexity of the build have an influence on the cycles to failure. Table 3 shows the results from the IST test and all five coupons tested passed the 500 cycles test. This test also confirms and agreed with the 6X solder shock test. Figure 9 shows a cross-section of a through-hole with 22 layers extracted from the IST test panel af- ter plating. Conclusions An excellent formula was developed for DC copper metallization for hoist lines and VCP applications. The operating CD range is 10–30 ASF where, micro distribution of ≥85% for AR 8:1 is achievable. Deposits were bright and duc- tile and also met IPC standards for the prop- erties such as tensile strength and elongation. The thermal characteristics of plated copper also met the IPC standards and showed no fail- ure during the solder shock tests. Coupons also passed the 500 cycles in IST testing. All the or- ganic additives can be easily monitored by in- dustry CVS analysis. PCB This paper was originally presented at the IPC 2017 APEX EXPO conference and was published in the proceedings. Figure 9: Cross-sections of IST 22-layer through-holes plated at 10 ASF with 2.4 mm test panel. Table 3: Interconnect Stress Testing (IST) data. HIGH-THROW DC ACID COPPER FORMULATION FOR VERTICAL CONTINUOUS ELECTROPLATING PROCESSES

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