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66 The PCB Magazine • April 2016 and UL746B 20A [1] to estimate the high-temper- ature test boundary for long-term aging of PWB laminate material capabilities. Pre-screen data is used as an initial sort on best performing mate- rial. Criteria evaluated include highest dielectric strength, lowest overall degradation, lowest per- cent change in degradation, and anomalous or unexpected behavior (indicating instability). DfR Solutions completed the first portion of testing, consisting of a 500-hour prescreen ag- ing test of five materials at four different tem- peratures. Results from the 500-hour prescreen were used to adjust test parameters for the next phases of testing. Data collected includes weight loss, sample thickness, dielectric break- down voltage for baseline and sample coupons after exposure to for different temperatures for 500 hours. Five data points were collected per measurement point. Each material was tested to collect ten base- line data points in the X-Y, Z-Core and Z-Fill areas of the test vehicle. Using the published electric strength data—the estimated dielectric withstand voltage (DWV) failure point was cal- culated. Average, standard deviation, and range were calculated. A summary of the baseline av- erages is presented below in Table 3. Laminate C and Laminate D have the highest dielectric withstand voltage values compared to the oth- ers in the test set. long-term thermal reliability of pCb materials Figure 4: Sample racking, racks in oven, and sample location naming scheme. Figure 5: Flow diagram of testing sequence for controls and test vehicles for Phase I through III along with sample schedules for the 1000-hour test and two-year long-term test.