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84 The PCB Magazine • July 2016 tion is that temperature at which the resin ma- terial loses 5% or more of its weight. The weight loss may have deleterious effects on the perfor- mance and reliability of the PTH. This author suggests that for high-reliability performance requirements, choose a resin material with a Td of 340°C or above. An IPC test method has been developed to determine Td [2] . Certainly there are other factors that con- tribute to PTH reliability. And these will be the subject of a future column. But for now, Figure 4 shows that there are stark differences in IST failure results when comparing low Td material with higher Td. Summary Understanding and controlling the many factors that influence PTH reliability is a com- plex and often not absolute process. Part 1 of BUILDING RELIABILITY INTO THE PCB, PART 1 this column provided some background into failure mechanisms in the PTH. The concept of Td was introduced, as well as how that resin property impacts PTH reliability. PCB References 1. Correspondence with Bill Birch, PWB In- terconnect Solutions. 2. IPC Test Methods Manual TM-650, www. ipc.org. Michael Carano is VP of technol- ogy and business development for RBP Chemical Technology. To reach Carano, or read past columns, click here. Figure 4: IST comparison of two resin systems—similar Tg but different Td.