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74 The PCB Magazine • April 2016 est dielectric breakdown strength be- fore thermal aging while Laminate E has the lowest. In general, the Z-Core was more robust with respect to dielectric break- down. The Z-Fill (prepreg layer) was the less robust even though it thick- ness was almost twice that of the Z- Core. These results are summarized in Table 7. The % retention was calculated us- ing the same methodology that was used calculate T4 for the 1,000-hour test using the 500 hour pre-screening data. The 50% EOL point was calculat- ed for each temperature. An Arrhenius plot was generated for each material plotting 1/T (K) on the X-axis vs. Log long-term thermal reliability of pCb materials Figure 9: Graphical representation of baseline average breakdown strength, V/mil. Table 7: Comparative Analysis Baseline Average Breakdown Strength—Board location. Table 6: Comparative Analysis Baseline Average Breakdown Strength—laminates. Table 8: Temperatures for 1,000-Hour Test Based on 500-Hour Test and Input from laminate Suppliers.