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44 The PCB Magazine • March 2014 ment in capacitance value for the outer layers as the test progresses. This was particularly evi- dent in case of material 'E' which showed an improvement in capacitance value between 6x260°C and at the end of test measurements. Since all materials were stored under the same conditions, it leads us to believe that material is more hydroscopic. Also, 0.8 mm pitch showed early capacitance failure for material 'RA' indi- cating that either the material bond was com- promised during drilling or that the material bond strength was not the best. IST Test Analysis A summary of test results is shown in Table 4. The data shown is cycles to failure for six cou- pons of each material type. Any failure that was process related has been taken out. In our IST results, material 'RB' showed good cycles to failure but when sectioned we saw the extent of damage to the material in Figures 6–9. The degree of delamination seen in Figure 10 agrees with the results seen in capacitance mea- surements of these coupons. The material had degraded to a stage where further cycling would not have had any further degradation. BEHAVIOR OF MATERIALS IN THE MANUFACTURING ENVIRONMENT continues table 4. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10.